I need to bye a new graphics card. The two affordable models for me are Nvidia FX 5500 & ATI R9550 (about $100). I don't really know many things about them, and can't choose which one is the best! Any suggestion or advice would be very helpful!
Welcome to the forums! My advice is, save up for a better card. I have a radeon 9550 that I bought with my PC, had it for a month or two and I'm going to get a better videocard for my birthday, probably a gf6800LE. Just save up a little longer, and go and get yourself a really good videocard instead of a "meh it's ok"-style videocard.
I would probably stay away from the GeForce FX - it's not great and you will get inconsistent performance across games.
the 9550 aint much better. IF you want gaming on the cheap, get a vanilla 9600 and oc it to higher hell. 275-440 Core on mine, stock cool .
Have to agree with the above. Try and get at least a 9600 (pro or xt would be loads bettr). Both the cards you mention are pretty poor for gaming.