15 minutes then Crash to main menu
 

Fellow Stalkers, i have an issue...please i need some assistance

i am only able to play multiplayer for 15 minutes at a time then i crash back to main menu, and every 1 of 5 times i crash and have to restart my computer...any suggestions or ideas why this is happening? any info is appreciated...here are my pc specs

dell dimension 8300
ati radeon 1950xt
2.79 Ghz, 3.25 GB of Ram

if anything else would be helpful please let me know.