computer not turning on with new gpu

werew

Honorable
May 8, 2013
19
0
10,510
so i have a Cooler Master eXtreme Power Plus 500w and a radeon hd 7850, and everytime i put the gpu in the computer wont power on. i am currently using my friends gpu (8600 gts i believe) and it powers on with the same 6pin cable. idk if my psu is underpowered because it previously worked without problems and the computer would do this a couple time but im not sure how i fixed it and this time im just lost.
 

werew

Honorable
May 8, 2013
19
0
10,510

unfortunately the only other psu i have is only 350 watts.