Are you one of those people that watched that video on youtube called want to see what happens when you go into your hard drive and delete the folder called windows , well if you did, Congratulations on deleting your whole computer from your HDD , you need to reinstall your OS!!!
The only other way that i know that it can be courrpt besides the user del it, it could have been a virus that you provably picked up from the net, New viruses these days del stuff from your pc, it targets either the system32 folder or the windows folders watever they can do to damage someones PC!!!!
Well like the user above stated try to do a system repair from the WIN setup disc, or try to go into safe mode and try to do a system restore from an earlier date, GL on fixing your problem