I recently purchased a PS3 with a few games from Ebay.
Only certain models are backwards compatible. I think the 40gb one is not, along with the 20gb. I know the 80gb is, I have that one.
I am currently hooked on Rainbow Vegas Six 2, my friend and I get on and play regularly. Luckily it was one of the games that came with my purchase. I traded in the other game, Turok, for Elder Scrolls. Glad I did, the Oblivion game is fun, just solo.
Mac