Win XP Freeze When Gaming

Hi all, I wonder if you guys have an answer for me please, I recently upgraded my graphics card from a geforce 2 mx prophet to a geforce 4 mx 440 (creative) since i upgraded windows xp freezes during games and the only way to get out of it is to reset the pc, My card only had a heatsink and no cooler so i moved to cards from below it so it had room and also put a thermal take silver orb on it so i dont think cooling is an issue. I have tried a clean xp install and drivers from 30.82 right up to 41.x beta. In normal day to day apps use i dont get any lock ups so it looks like a graphics card issue. I have recently installed win 2000 pro and ive only had time to play games for 3 hours (ut2003) and no problems but i really would like to get back to xp if i can. My system specs are below, thanks in advance guys.

Home built.

Athlon XP 1600+
320mb ram 1x256 + 1x64
maxtor 40 gig hd
maxtor 60 gig hd
geforce 4 440 mx
hercules gamesound fortisimo 2
belkin usb 2.0 card
16x memorex cdrw
toshiba dvd drive
ecs k7s5a mobo

forgot to mention that its not just ut2003 that locks, medal of honour, rtcw and star wars galactic battlegrounds all do the same...