Auto System Restart

Hey Guys And Galls,

just wondering if any of you new about this problem, i was playing a game and then all of a sudden my pc rebooted automatically and then at startup it said “windows has recovered from a serious problem” i didnt send the information but could anyone tell me as to why this is occuring and how i can make sure it doesnt happen again:

#PC Spec#

windows xp pro S2
Asus P4PE 845 X Series
Pentium 4 Intel 2.4 Processor
G-ForceFX 5600 256 Meg
1 Gig Of 400 Speed DDR Ram
Onboard Sound And Lan
40 Gig Harddrive (30% Used)