Computer Freezes When Accessing Hard Drive

The title is actually only a best guess, the problem started a few days ago when I was playing Halo Online. I had just started playing, so when my computer started to freeze up I figured it was the game. By freeze up I mean nothing would move, and no. combination of buttons did anything, sound was gone, it was completely hanging.

Not long after though, any game seemed to freeze my computer. Opening up my case and looking inside I discovered my video card was having trouble spinning its fan. The temperature read as normal (50 c or so) but it was the only thing that made sense.

Fast forward to today and I just finished installed a new video card. Yay. This didn't solve my problem though, in fact now when I tried to access My Computer it would freeze the system. Opening any folder would, actually.

Any suggestions?

Specs: Windows 8.1 64-bit AMD Athlon 64 X2 5200+ 4 GB DDR2 RAM AMD Radeon HD 6450 500 GB Seagate Hard Drive