Big problem with my radeon1950x Need help

hi i really need help and information on solving my video card problems. recently my pc has been crashing a lot, getting auto restarts, and recieving blue screens. I purchased this pc last year. usage is mostly on online games and other games which dont have high requirements on the video cards and ram. until recently i installed SERIOUS SAM2 my pc has started crashing a lot. i've already tried updating the drivers but problems still occur.

these are the problems.
-Crashes during game.
-auto restart even during in desktop mode.
-receive blue screen warning, error with ati2dvag , caught in infinite loop.
-when installing new drivers for video card, (ati radeon 1950x) catalyst 8.9 version) error message saying ""zero display service error""
-subsequently when turning on the pc, i get an error message saying " no driver installed for your video card."
-once when running a game programme recieved message saying "" your video card has been reset" ??

i'm away from home most of the week so i only have access to my computer on weekends so i thought i could rule out overheating as a problem.

Anyway this are my computer components that i use.
MS windows XP SP3
INtel Core2 DUO CPU E6750@2.66 GHZ 2.0GB RAM
RAdeonX 1950 PRo secondary
ASUS p5k-SE LGA-775
TOPOWER 450W SLI 20/24p
SAM SATA 20x DVD-RWinternal

p.s i really dont have much computer knowledge, .. Any help and information will be greatly appreciated... THANKS!!