My old MSI 8800 GTS OC was crashing and freezing my operating system. I heard from here that baking your video card in an oven is an option.
I had nothing to lose because the card was unusable and I didn't think it was going to work but... it actually did. I took off my heat sink, removed the old thermal tape, put it in the oven with the GPU facing up, and let it bake at 350 degrees for 10 minutes. I put on fresh thermal gel and remounted the heat sink and it works like new.
So if you have an old card laying around that doesn't work, try it out and post your results!