Serious problems

My pc keeps on restarting randomly and sometimes i get a blue screen where it say physical memory dump error at the bottom of the screen. How to fix this error. i have used different types of drivers and also reinstalled windows. Any help

 AMD 64 3400

X800gto

1GB Ram

350watt Power supply

Abit kv8 pro motherboard

Don't have anything overclocked do you? Did you update your drivers to the manufacturers latest? Have you upgraded or changed anything recently, such as a new part or changed a setting?