А что сообщается в Журнале событий -> Приложение?

Может быть это вам поможет, естественно все действия на свой страх и риск.
http://www.eventid.net/display.asp?eventid=11706&eventno=1831&source=MsiInstaller&phase=1
If you are having problems when installing the ".Net Framework", then read the following newsgroup post. However since this post suggests modifying the registry and other important directories, try to do a backup (or Restore point) before following this post.
From a newsgroup post: "The following is a "blanket solution" that has resolved many cases in my experience:
1. Make sure IIS is not running.
2. Uninstall the .NET Framework from Control Panel's Add/Remove Programs.
3. Delete following folders:
C:\WINNT\assembly
C:\WINNT\Microsoft .NET
4. Delete the following files
C:\WINNT\System32\mscoree.dll
C:\WINNT\System32\URTTemp\mscoree.dll
5. Delete the following registry keys:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Integration]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework SDK]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup]
6. In C:\WinNT\Installer do the following:
Switch to Details view.
Right-click on the Name column header and choose Comments from the pop-up list.
Find the .MSI file with the comment that says ‘Microsoft .NET Framework
(English)…’ and delete it.
7. Download (to your desktop) the .NET Framework (redistributable) from the link below. Once downloaded, run dotnetredist.exe and extract its contents (dotnetfx.exe) to your desktop as well.
8. Download .NET Framework SP2 (NDP10_SP_Q321884_En.exe) to your desktop. The download is also listed below.
9. Start|Run; type "msconfig" (without quotes) and click OK to start the System Configuration Utility.
10. Under the General tab, choose Diagnostic Startup.
11. Under the Services tab, find and add a check to Windows Installer.
12. Click Apply then Close.
13. Reboot when prompted.
14. Start | Run... type "%temp%" to get into your temporary directory. Delete all contents of the folder. At this point, reinstall the Framework by running DotNetFX.exe, then SP2. Note that the settings set in the System Configuration Utility will persist from boot up to boot up; to get back to normal startup you must select 'Normal Startup' in the utility and reboot. If Framework and SP2 go on successfully, you may need to use the Q306005 article to reset ASPNET mappings in IIS".