The PSU's that come with cases are generally garbage on the 12v lines. It could be your PSU, but it's prolly best to buy a new one anyway. Check out the
PSU 101 for some good suggestions. You could also just do a full re-install of windows if you want (a repair install SHOULD work fine though). Mind you if you do a full re-install (format and all) you will want to back up your data first.
The freezing could also be related to a virus/spyware/adware. Look in the security forum for some good programs to do a sweep of your machine, see if that happens to be the problem.