Irritating Vista issues: .Net and C++ Redistributable

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I recently switched my main HDD to boot Vista, and today I'm encountering errors when trying to run the majority of my programs. Anything associated with .NET (Paint.NET, Synctoy, etc) gives this error:

http://x020.uploaderx.net/x/Untitled.jpg

Furthermore, launching anything associated with MS C++ (Word 2007, etc) gives me this message:

http://x020.uploaderx.net/x/Untitled2.jpg

I've tried removing both packages and installing .NET 3.0 and the latest C++ package, but the errors persist. What's wrong here?

 

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Thanks to all the advice posted here, I found a solution: reformatting.

This time the install went better, but I'm getting random freeze-like behavior every ten minutes or so, where the computer will be unresponsive for a minute or more (elements on-screen are clickable however) and then suddenly the hard drive will spring back into action and keep working on whatever it was doing. The odd thing is that downloads and such keep downloading, but I just can't launch new programs, click the start menu, or anything of that nature. Very odd.