That doesn't sound good.. I'd re-install the os again, if you still get problems your HDD might have corrupt sectors. If you can boot into safe mode and do a scandisk you may be ok but otherwise re-install and start again.
sounds like a good idea. If you could attach the HDD thats giving the problem to another pc (maybe a friend could help?) you could try and analyse it to see if it's on it's way out... Anyway whatever you end up doing, I hope it goes well for you..