With that much seriously hardcore beta software on there, you would be best off formatting and reinstalling. FDISK, man.

Seriously though, once you've rebuilt the system, make a Ghost image of it for future reloading. Stash that on a DVDR along with a trusty Ghost boot disk. Then you can try out all the risky software (WinFX, DOTNET beta, etc) and just reghost.

I actually have my Windows partitions set up so C:\ contains only Windows system files (apps on D:, storage on E: and F:). If I'm doing something risky, I'll make a Ghost backup of C:\ first.