Reboot, Reformat, Reinstall. Fixes almost any serious Windows problem. Usually due to:

#1 A bad registry

#2 DLL Hell

#3 Bad Hard Drive partition (run FDISK, delete the partition, recreate it, reformat)

#4 A Virus or Trojan messing things up and AV and Cleaner software cannot remove it.

#5 Bad System files.

Sometimes you can just delete the registry or part of it and do a reinstall, that is if you know which part of the registry is bad.

Of course doing a RRR and using Linux instead will provide different results. :)