one thing that i have seen happen before is that people get spyware and go crazy deleting things some times different programs share files called dll files dynamic linking library files sometimes spyware may share files with legitimate programs and if you delete the spyware the legitimate file will no longer work spybot has an undo function in case you do something like this and xp makes system restore points when spybot does stuff but usually when you delete dll files that are important windows will give you errors