1) Download the Stebner .NET Cleanup tool

http://blogs.msdn.com/b/astebner/archive/2008/08/28/8904493.aspx

http://blogs.msdn.com/cfs-file.ashx/__key/CommunityServer-Components-PostAttachments/00-08-90-44-93/dotnetfx_5F00_cleanup_5F00_tool.zip

2) Run the cleanup tool and select the option to remove ALL .NET Frameworks.

3) Once tool is complete it should ask you to reboot. You will want to reboot

Note: If you get any errors .NET Cleanup tool, try using the Windows installer cleanup tool:
http://www.softpedia.com/get/Security/Secure-cleaning/Windows-Installer-CleanUp-Utility.shtml
remove all instances of .NET fw. Then re-run the Stebner tool, removing all again. Reboot.

Once rebooted, your PC should now be free of all .NET things

5) Now, download .NET fw 3.0 and install
http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=31

6) Download and install .NET fw 3.5/SP1 

http://www.microsoft.com/download/en/details.aspx?id=22

7) Reboot just do it.

8) Now open IE and go back to Windows/Microsoft Update site. Select the update for kb951847 it should now install properly

9) Once installed, reboot and return to Update site and let the rest of the .NET updates get installed