In a computer, there are various methods of storing information.  Information can be stored in the processor cache, RAM, hard disk, etc.  It can be faster to request information from a storage medium that is smaller.  However, this smaller storage medium cannot fit all the possible information that can be requested.  So the idea is to insert a portion of the data into the faster, smaller medium (the cache) and the rest into the slower, larger medium (main memory).

If a request is made and the data is not available in the faster, smaller medium first, then the data will be read from the slower, larger medium – this is what is known as a cache miss.

Given that all the data cannot possibly live in the cache, there must be a way to minimize the amount of times that the data must be read from the main memory.

Optimal Caching – Farthest-in-Future

The Algorithm

The idea is that there is an algorithm that minimizes the amount of cache misses that occur for a set of requests.  The Farthest-in-Future Algorithm evicts the item in the cache that is not requested until the farthest in the future.  For example, given the following cache with items “a” through “f”.

It is clear that “g” does not exist in the set of cache items and so when “g” is requested, a cache miss will result. An item will be evicted because “g” is not in the cache.  According to the Farthest-in-Future Algorithm, element “f” will be evicted since it is the one that will be used furthest in the future.

Definitions

Cache Miss – Occurs when it is necessary to bring in an item from the main memory into the cache

Schedule – A list that contains, for each, request, which item is brought into the cache, and which item is evicted

Reduced Schedule – a schedule that only brings in an item when there is a request for that item – so a non-reduced schedule would bring an item into the cache outside of a request for that item

Theorem

To be shown:

Farthest-in-Future is the optimal algorithm that minimizes the number of cache misses.

To prove this, let’s say there is a schedule SFF that follows the Farthest-in-Future Algorithm and that there is a schedule optimal S that has a minimum number of cache misses. It can be shown that it is possible to transform S into SFF by performing a series of evictions without increasing the number of cache misses.  Since S^* is already optimal, and the number of cache misses did not increase, then SFF must be optimal.

To perform one transformation, the statement below can be used.  Right now, it isn’t all that clear why this is necessary, but it should become clearer further on.

Let S be a reduced schedule that is the same as SFF for the first j requests, then there is a reduced schedule S’ that is the same as SFF for the first j+1 requests, and incurs no more misses than S

Proof

Let’s say the cache at the start looks like this.  S and SFF have the exact same contents (this is what was defined in the previous section).

Given a schedule S, it can be shown that any request can be made, and the resulting schedule would be equal to the ideal algorithm and does not increase the number of cache misses.  Essentially, we want S = S’ = SFF after a request is made and that the number of cache misses have not increased.  If this can be shown for all different scenarios that items are requested, then Farthest-in-Future is the ideal algorithm.

Case 1: Item Is Already in the Cache

Now let’s say the next item to be requested is item “d”.  It is clear that this item exists in both caches and no evictions are necessary.  Since no evictions are necessary, SFF does not change.  It was specified in a prior section that there is a schedule S’ that equals SFF, which incurs no more misses than S.

Here, S = S’ because no changes had to be made to the cache and there were no cache misses.  After the request for item “d”, S = S’, each with zero cache misses, which is a valid outcome.

Case 2: Item Is Not in the Cache, S and SFF Evict the Same Item

Let’s say the next item to be requested is item “e”.  Neither cache has this item, so an eviction will have to be made.  Let’s also say SFF and S both choose to evict item “a” to make room for “e”.  It was specified in a prior section that there is a schedule S’ that equals SFF, which incurs no more misses than S.

Here S = S’ because S and SFF both evicted the same item.  Both S and S’ each have one cache miss (no increase relative to one another), which is a valid outcome.

Case 3: Item Is Not in the Cache, S and SFF Each Evict A Different Item

This is where the proof can become more confusing (as if it isn’t already).  Let’s say the next item to be requested is “e”.  Let’s also say that the ideal algorithm, SFF, evicts “a” and S evicts “b”. It was specified in a prior section that there is a schedule S’ that equals SFF, which incurs no more misses than S. This means that in order to get S’ = SFF, S’ should evict “a” in order to match with SFF.

Here, S does not agree with S’ = SFF.  Essentially, these two schedules behave the same, so long as future requests do not request items “a” or “b”.  This shows that there is a schedule S’ that equals SFF, but it is not known whether or not S’ has no more cache misses than S, since “a” or “b” can be requested in the future, which can determine whether S or S’ has more cache misses.  From this point onward, S and S’ behave the same until one of the following happens:

Case 3a: Item Is in SFF, But Not S; S Evicts “a”

Let’s say eventually item “b” gets requested.  In this case, S’ and SFF do not need to change.  All S has to do is evict “a” to make room for “b”.  In this case, S has two total cache misses (from request “e” and “b”), while SFF and S’ each have only one cache miss, thus fulfilling the cache miss requirement.

Case 3b: Item Is Neither in SFF Nor S

Let’s say eventually item “f” gets requested.  S’, SFF, and S all need to make an eviction. S’ and SFF can evict “b” to make room for “f”, and S can evict “a” to make room for “f”.  In this case, each schedule as two cache misses, thus fulfilling the cache miss requirement.

Case 3c: Item Is in SFF, But Not S; S Evicts Item Not Equal to “a”

Let’s say eventually item “b” gets requested and S evicts an item that isn’t “a”, say “c”.  Now, SFF and S’ both already have “b” in the cache.  In order to synchronize S and S’ to make them comparable to see how many cache misses each have, S’ and SFF will evict “c” to make room for “a”.

Since “a” is being brought into the cache without a request for “a”, this makes S’ and SFF no longer a reduced schedule.  However, the proof calls for S’ and SFF being a reduced schedule.  Fortunately, it is possible to transform an unreduced schedule into a reduced one.  In this case, each schedule has two cache misses, thus fulfilling the cache miss requirement.

Case 3d: Item Is Not in SFF, But in S

The only item that is in S and not SFF is item “a”.  SFF had evicted it initially at the beginning of Case 3.  Since SFF had evicted it, it must have been the item that would be requested furthest into the future.  Therefore, it is not possible for item “a” to be requested before other items.

After going through all possible eviction decisions that the schedules can do, it was shown that for each scenario, there was indeed a schedule S’ = SFF, where the cache misses incurred in S’ no more than S.

Link: http://www.heerengandhi.com/2009/07/29/firefox-icon-went-missing-in-windows-7-heres-a-fix/comment-page-1/

UPDATE: This set of instructions works for the Office 2010 Technical Preview as well.

Based on: https://answers.microsoft.com/en-us/msoffice/forum/all/trying-to-install-office-2010-but-getting-error/4a5e022f-13f1-42bb-ad66-f6dccfd44d40

To automatically uninstall the 2007 Microsoft Office suite, follow the steps in the following Microsoft Knowledge Base article: http://support.microsoft.com/kb/971179/

How do I uninstall the 2007 Office suites if I cannot uninstall it by using the “Add or Remove Programs” feature?

The steps provided in the ‘More Information’ section of this article provide the details of the removal performed by the solution in 971179.

You may find it easier to follow the steps if you print this article first.

First, verify that you cannot uninstall the 2007 Microsoft Office system by using Add or Remove Programs (or Programs and Features)

To verify that you cannot uninstall the 2007 Microsoft Office system by using Add or Remove Programs (or Programs and Features in Windows Vista), follow these steps.

For Windows XP or Windows Server 2003:

1. Click Start, click Run, type control appwiz.cpl in the Open box, and then press ENTER.
2. Click to select the 2007 Office system product from the application list, and then click Remove.

For Windows Vista:

1. Click Start, type prgrams and features in the Search box, and then press ENTER.
2. Click to select the product to be uninstalled from the listing of installed products, and then click Uninstall/Change from the bar that displays the available tasks.

If you were able to uninstall the 2007 Microsoft Office system by using Add or Remove Programs, you are finished. If you were unable to uninstall the 2007 Microsoft Office system, you may have issues with the Add or Remove Programs dialog box, or some 2007 Microsoft Office components may not be uninstalled. In these cases, you may be unable to reinstall the 2007 Microsoft Office system. Go to the next section to uninstall the 2007 Microsoft Office system by using an alternative method.

If Add or Remove Programs does not uninstall the 2007 Microsoft Office system, use this alternative method to uninstall

Use this method only if the Add or Remove Programs method did not work for you. Using this method does not completely uninstall the 2007 Microsoft Office system. After you use this method, you can reinstall the 2007 Microsoft Office system.

Note You must be logged on to Windows with a user account that is a computer administrator to complete this method. If this is your personal computer, you are likely already logged on with an administrator account. If this is a computer that is part of a network, you might have to ask the system administrator for help.

To uninstall the existing 2007 Microsoft Office system if you cannot uninstall it by using the Add or Remove Programs feature, follow these steps:
Step 1: Remove any remaining Windows Installer packages of the 2007 Microsoft Office system:

1. Click Start, click Run, type installer, and then click OK.
   This process opens the %windir%Installer folder.
2. On the View menu, click Details.
   Important To use the View menu in Windows Vista, you must press the ALT key first to display the menu bar, and then click the View menu.
3. On the View menu, click Choose Details.
4. Click to select the Subject check box, type 340 in the Width of selected column (in pixels) box, and then click OK.
   Note It may take several minutes for the subjects to appear next to each .msi file.
5. For Windows XP or Windows Server 2003, on the View menu, point to Arrange icons by, and then click Subject.
   For Windows Vista, on the View menu, point to Sort By, and then click Subject. In Windows Vista, a User Account Control dialog box may be displayed with the following warning:
   An unidentified program wants access to your computer

   Click Allow when you see this warning message.

6. For each .msi file where the subject is “Microsoft Office Product_Name 2007,” right-click the .msi file, and then click Uninstall.
   Note Product_Name is a placeholder for the name of the 2007 Microsoft Office product.

Step 2: Stop the Office Source Engine service:

1. For Windows XP and Windows Server 2003, click Start, click Run, type services.msc in the Open box, and then click OK.
   For Windows Vista, click Start, click Start Search, type services.msc, and then press ENTER.
2. In the Services window, determine whether the Office Source Engine service is running. If this service is running, right-click Office Source Engine, and then click Stop.
3. Close the Services window.

Step 3: Remove any remaining 2007 Microsoft Office installation folders

1. For Windows XP and Windows Server 2003, click Start, click Run, type %CommonProgramFiles%\Microsoft Shared in the Open box, and then click OK.
   For Windows Vista, click Start, click Start Search, type %CommonProgramFiles%\Microsoft Shared, and then press ENTER.
   Note On a computer that is running a 64-bit version of Windows Vista, type %CommonProgramFiles(x86)%\Microsoft Shared, and then press ENTER.
2. If the following folders are present, delete them:
   • Office12
   • Source Engine
3. For Windows XP and Windows Server 2003, click Start, click Run, type %ProgramFiles%\Microsoft Office, and then click OK.
   Note On a computer that is running a 64-bit version of Windows XP, type %ProgramFiles(x86)%\Microsoft Office, and then press ENTER.
   For Windows Vista, click Start, click Start Search, type %ProgramFiles%\Microsoft Office, and then press ENTER.
   Note On a computer that is running a 64-bit version of Windows Vista, type %ProgramFiles(x86)%\Microsoft Office, and then press ENTER.
4. On the root folder of each hard disk drive, locate and then open the MSOCache folder. If you cannot see the MSOCache folder, follow these steps:
   1. Open Windows Explorer, and then on the Tools menu click Folder Options.
   2. Click the View tab.
   3. In the Advanced settings pane under Hidden files and folders, click Show hidden files and folders.
   4. Click to clear the Hide protected operating system files check box, and then click OK.
5. Open the drive_letter:\MSOCache\All Users folder, and then delete every folder that has the following text in the folder name: 0FF1CE

   Note This text contains a zero and a one for the letters “O” and “I.”

Step 4: Remove any remaining 2007 Microsoft Office installation files

1. For Windows XP and Windows Server 2003, click Start, click Run, type %appdata%\microsoft\templates, and then click OK.
   For Windows Vista, click Start, click Start Search, type %appdata%\microsoft\templates, and then press ENTER.
2. Delete the following files:
   • Normal.dotm
   • Normalemail.dotm
3. For Windows XP and Windows Server 2003, click Start, click Run, type %appdata%\microsoft\document building blocks\Language_ID, and then click OK.
   For Windows Vista, click Start, click Start Search, type %appdata%\microsoft\document building blocks\Language ID, and then press ENTER.
   Notes
   • If you cannot open this folder because the folder does not exist, go to step 6.
   • Language_ID is a placeholder for the four-digit number that represents the language of the 2007 Microsoft Office system. For example, if you use the English version of the 2007 Microsoft Office system, the Language_ID value is 1033. If the Language_ID is not known, type %appdata%microsoftdocument building blocks, and then open the subfolder in that location.
4. Delete the Building blocks.dotx file.
5. For Windows XP and Windows Server 2003, click Start, click Run, type %temp%, and then click OK.
   For Windows Vista, click Start, click Start Search, type %temp%, and then press ENTER.
6. On the Edit menu, click Select All.
7. On the File menu, click Delete.
8. For Windows XP and Windows Server 2003, click Start, click Run, type %AllUsersprofile%\Application Data\MicrosoftOfficeData, and then click OK.
   For Windows Vista, click Start, click Start Search, type %AllUsersprofile%\Application DataMicrosoftOfficeData, and then press ENTER.
9. Delete only the Opa12.dat file.

Step 5: Remove the registry subkeys of the 2007 Microsoft Office system

Important: This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: http://support.microsoft.com/kb/322756/

1. Locate and then delete the registry subkeys of the 2007 Microsoft Office system if they are present. To do this, follow these steps:
   1. For Windows XP and Windows Server 2003, click Start, click Run, type regedit, and then click OK.
      For Windows Vista, click Start, click Start Search, type regedit, and then click OK.
   2. Click the following subkey:
      HKEY_CURRENT_USER\Software\Microsoft\Office\12.0
   3. On the File menu, click Export, type DeletedKey01, and then click Save.
   4. On the Edit menu, click Delete, and then click Yes to confirm the deletion.
   5. For each registry subkey in the following list, repeat steps 1a through 1d. Change the name of the exported key by one for each subkey.
      For example, type DeletedKey02 for the second key, type DeletedKey03 for the third key, and so on.
      Note In the following registry keys, the asterisk character (*) represents one or more characters in the subkey name.
      32-bit versions of Microsoft Windows:
      • HKEY_CURRENT_USER\Software\Microsoft\Office\12.0
      • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\12.0
      • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Delivery\SourceEngine\Downloads\*0FF1CE}-*
      • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*0FF1CE*
      • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UpgradeCodes\*F01FEC
      • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-18\Products\*F01FEC
      • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ose
      • HKEY_CLASSES_ROOT\Installer\Features\*F01FEC
      • HKEY_CLASSES_ROOT\Installer\Products\*F01FEC
      • HKEY_CLASSES_ROOT\Installer\UpgradeCodes\*F01FEC
      • HKEY_CLASSES_ROOT\Installer\Win32Assemblies\*Office12*

        64-bit versions of Microsoft Windows:

      • HKEY_CURRENT_USER\Software\Microsoft\Office\12.0
      • HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\12.0
      • HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\DeliverySourceEngineDownloads\*0FF1CE}-*
      • HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*0FF1CE*
      • HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Installer\UpgradeCodes\*F01FEC
      • HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-18\Products\*F01FEC
      • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ose
      • HKEY_CLASSES_ROOT\Installer\Features\*F01FEC
      • HKEY_CLASSES_ROOT\Installer\Products\*F01FEC
      • HKEY_CLASSES_ROOT\Installer\UpgradeCodes\*F01FEC
      • HKEY_CLASSES_ROOT\Installer\Win32Assemblies\*Office12*
2. Locate the following registry subkey:
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

   Note On a computer that is running a 64-bit version of Windows, locate the following registry subkey instead:

   HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall
3. On the File menu, click Export, type UninstallKey01, and then click Save.
4. Under the Uninstall subkey that you located in step 2, click each subkey, and then determine whether the subkey has the following value assigned to it:
   • Name: UninstallString
   • Data: file_name path\Office Setup Controller\Setup.exe path
     Note In this example, file_name is a placeholder for the name of an installation program, and path is a placeholder for the file path.
5. If the subkey contains the name and the data that are described in step 4, click Delete on the Edit menu. Otherwise, go to step 4.
6. Repeat steps 4 and 5 until you locate and then delete every subkey that matches the name and the data that are described in step 4.
7. Close Registry Editor.

Step 6: Restart the computer

Restart the computer. If the uninstall was successful, you are finished and can now reinstall the 2007 Microsoft Office system if you want. If the uninstall was not successful, go to the “Next Steps” section.

Additional registry information

HKEY_CURRENT_USER\Software\Microsoft\Office\Common\UserInfo

Shadow subkeys for Windows Server 2003 and for earlier versions of Windows Server:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Terminal Server\Install\Software\Microsoft\Office\12.0

Shadow subkeys for Windows Server 2008:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Terminal Server\Install\Software

Source: http://support.microsoft.com/default.aspx/kb/928218