My friends HP system.
AMD64 X2 4400+ AM2
2 gigs of ram
Vista Home Premium 32-bit
I installed an eVGA GeForce 7600GT (identical to ours) in his system, and downloaded the latest drivers.
The performance was nearly identical to what I get.
The drivers however, took a long time to install. Like, it would just sit there, the progress bar, for like three minutes, then it would go. It was all fine after that though.
He's played (and i've watched to see for myself) Halo, Half-Life2, and FarCry with good results.