Gee, I upgraded
to the Radeon 9550. It works fine.
However, at the same time, I decided to upgrade my RAM from 512mb to over a Gig. That's when the trouble started. After several weeks of various tech support people giving me 'advice', and totally re-formatting my HD three times (losing a ton of good stuff, of course), I took the new RAM out and went back to the original 512mb and life is now good - no, WONDERFUL! I never should have bought the RAM.
Oh, and my first new Radeon card was defective but Best Buy swapped it out, no questions asked. Good for them!