San Andreas problems

I recently bought Gta:San Andreas for PC and installed it.Everything went smoothly when running the game until my pc wants to shutdown after a few minutes of gameplay and gives me some error message involving driver_irql_not_less_or_equal and cmuda.sys and restarts after dumping the physical memory.

PS: My pc specs r :
p4 3.2 ghz
512 ram
ati 256mb radeon 9250
120gb hdd
directx 9c
with 5.7 catalyst drivers
So it should run but it doesn't thanx for the help in advance