Windows – MSVCR100.dll missing error even its there

You're better off not removing them. C++ Redistributables are installed by programs which depend on them. See this thread for a similar question.

Of the versions you have listed, each one could either be a patch (in which case you'd be removing bug fixes and features by removing it) or a new version (in which case you'd be removing a redistributable that a program depends on). In either case, removing it would be unwise unless you have some real need to do it.

I realize that this question is likely no longer relevant to OP but just wanted to post my answer here in case it is helpful to anyone else.

I had this error earlier today on my 64-bit Windows 7 Pro (after uninstalling an application called PinnacleMyDVD I was not longer able to launch Outlook, MS Access, and some other apps).

I my case Windows event viewer displayed the following error:

Activation context generation failed for "C:\Program Files (x86)\Microsoft Office\Office14\OUTLOOK.EXE.Manifest". Dependent Assembly Microsoft.VC90.CRT,processorArchitecture="x86",publicKeyToken="1fc8b3b9a1e18e3b",type="win32",version="9.0.30729.1" could not be found. Please use sxstrace.exe for detailed diagnosis.

After reading through some of the other answers on this site, I decided to download and install the Microsoft Visual C++ 2008 SP1 Redistributable Package (x86) from here. This did not however resolve the issue.

One of the answers though pointed to this Microsoft article which is largely for Vista but also has a paragraph for Other versions of Windows (the instructions are practically the same for Vista and other versions, the only difference being the expected location of the registry keys).

According to the article the location of the registry key for non-Vista versions is: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\SideBySide\Winners

Anyway, I had already checked my Windows\winsxs directory after reinstalling the C++ redistributable, and found that it had a folder with a name that closest matched the parameters in the Windows event text: x86_microsoft.vc90.openmp_1fc8b3b9a1e18e3b_9.0.30729.1_none_118a7387f9d14a82

In this case it looked like the string 9.0.30729.1 in the folder name was the version of the file in that folder.

So I followed the instructions in the Microsoft article mentioned above, and changed my registry key to point to that version as shown in below screen shot.

After this the error was gone.