For GTA up to now my kit is great.
AMD 3000+ Chip w/ 1 gig ram
40 gig boot drive (OS & Drivers, User files)
200 gig data drive (Games, MP3s & backups here)
--- If you can afford the second hard drive, do it. you can a lot of headaches if you have to do a wipe & reload.
DVD r/rw + backup cd r/rw
Soundblaster live (older) + Altec Lansing 5.1 (not in use at the moment, half my speakers disappeared in the last move)
N-vidia 5500 w/356 meg
XP pro, service pack 2 (I think they finally fixed it, installed SP2 a month ago)
AVG free. Download form AVG site, supported w/ regular updates. If you can afford the pay version, it has extras. --- Between this & Windows Defender, I haven't had any thing get in.
All my GTAs fly on this machine & most of the components can be had reasonable (possibly cheap if you have access to used parts).
Godfather, Mafia, Unreal tournament, Lego Star wars & also look & run great. Scarface, not so much...
If you're on a budget, this kit should play most of the current games.
Good Luck