Saphire ati radeon x1950xt problems.

heey,

i have an saphire ati radeon x1950xt and after a while my pc just reboots when playing high end games. i think it is an heat issue because i have a really ugly standard family case. but i was wondering if it could also be a power issue (or can't cool good enough because lack of power) because i read that it was quite a power hungry card.

the weird thing is that this problem didn't occur like after half year of using this system.

system:
core 2 duo E6600
gigabyte 965P-DS3
DDR 2 mem (PC2-6400) (2x 1024MBytes)
cooler master 430 W i green power
HD: samsung spinpoint (T166?) 500gb