Radeon 9800 SE graphics card HELP!!

I use the radeon 9800 se card on my pc - Im running xp - have a amd athalon xp 2500+ chip.
My problem is the system run fine until i play a game i.e. at the moment SIMS 2 for my daughter and tiger woods for me - the game plays fine for about 5-10 minutes then my system just shuts off and i have to disconnect it from the mains before i can re-boot it. I've downloaded the latest omega 2.5.97 drivers but it still happens. Is my graphics card knackered and why does it keep crashing. any help would be appreciated.

 

It could be various things (most commonly faulty/inadequate PSU, BAD/incompatible RAM, overheating).
But before going any further, check the "Hardware' forums as similar issues had been posted and resolved previously, see if any of them would help you out, if not then post detailed info on your system including any changes/modifications you have done to the OS, Hardware, etc. prior to problem...