This sort of error is rather hard to diagnose since windows gives very cryptic erroe messages. Go to START, to RUN and type in "SFC" in the box. And click OK. This starts System File Checker and will report if any critical system files that have been corrupted. If that doesn't help any, reinstall Windows. It won't over-write your settings/desktop/programs but it will restore any bad files.
-=S_Klass=- I tweak... therefore I am.