It's fine for everything, apart from very demanding games (like first person shoot 'em up). I still have a TNT card and I am OK with it (had bought a GF3 and returned it for getting something else).
I believe that it works with WinXP, nVidia's drivers can be used for TNT-TNT 2 cards. It will be definitely better than the ATI 8MB.
Since it's free, go for it!