pc shuts down, upgraded gpu

Amit16

Honorable
Aug 26, 2013
1
0
10,510
Hi all, I'm not sure where to put this since this is my first post.
But anyways, I just purchased a nividia gtx 660ti from a Fry's and it was an open box and was the only one remaining. And this was my first gpu switch since I built the pc. But after I installed the gpu, the pc is now turning off every 5 secs. So at first i thought it was the card and tried to put my old gpu back in and the same thing happened. One thing that i found weird was that i left my pc off for about a day and the pc lasts just enough until 50% of the drivers have installed and shuts off.
I really need help with this and thanks in advance.
P.S. My psu also is 750w so i dont think it is a psu problem.
If you guys need more pc specs just ask