Hmmm...
Things you should do:
Clean up your PC. An air blower should work (Not a warm one! A normal temperature one with cold air should work.) and like blow everything out. Do not set it too high, but high enough to blow away the dust!
Look if it works then... If you still have it... well... Use a system restore! the last one you have, it might solve the problem.
And as last solution:
I would say: reinstall windows, and this time install programs slowly, like evey 3 days one program to see what is causing the problem. (Not counting the programs you need, but when you installed those, wait some days as sometimes they might cause the problem too)
But do it only if you really do not get a solution...