Help, my PC has started freezing up. Mouse/keyboard stop responding. H

Help, my PC has started freezing up. Mouse/keyboard stop responding. Have to restart.
I'm using Vista Ultimate 64, I had installed updates earlier today and tried adding another hard drive through disk management and then things start freezing when I tried installing a game on the new drive. I've done system restore, uninstalled the windows updates that had installed today and removed the new hard drive from disk management. It is once again unallocated. But my PC still freezes up shortly after being on for a while. I tried unplugging and plugging back in the usbs, no help. What should I do? it worked fine yesterday. My I think my bios version is 1504.

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