Re: Video Card overheating
If I had to guess, I'd say you're right about the age/power. Replacing it might help, but like you said it could also be the PSU.
If you want something cheap to just get the job done, I'd try something like this:
ETA: That's assuming you have the slot for it. I thought the 8800GT was PCIe 2.0, but wasn't sure.
Yada, yada, yada. Blah, Blah, Blah.