The three R's, RRR
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. :)
"Lady I only speak two languages, English and Bad English!" - Corbin Dallas "The Fifth Element"