Computer dropping frames suddenly?

I own a gaming computer with the following specs:
i7 3770k
Sapphire Radeon 7770
Gigabite Mobo
8 GB Corsair Vengance Ram
128 GB SSD
and an external HDD for all my games.

My computer has (in one day) gone from 60FPS on Black Ops 2 to 8 FPS no matter what settings I choose! I.e. I'll get 8 fps on 800x600 and 8 fps on 1920x1080. Tht only game not (as badly) effected as bad as all my other games are, is Minecraft, which previously got 211 FPS and now gets 38 FPS. FYI I have never overclocked, and I just did a virus scan using norton and found 2 viruses, but problem still persists, and I'm now considering nuking my SSD and reinstalling windows. And advice will be great, thanks brothers!

Reinstall your graphics driver with the most current available. It may have corrupted, or your computer might have switched to generic because it couldn't find it. Also, this is a wild guess. I have never heard of this happening… Ever.