Recently I put in a new GRAPHICS card for my computer (Radeon HD 7770) but now my computer wont start up. It loads up completely but about 3 minutes after boot, the screen goes blank. It seems to go the colour that the screen was mostly made up of when it turned of. I have no mouse and if I am listening to ANYTHING as the computer turns off, it hums in the pitch that the sound is. I then have to turn the computer off by holding the power button. The computer works when I put it in safe mode though. Im just wondering if any of you guys have any idea what could be wrong with my computer and maybe help me

Specs:

Windows 7 32 Bit
Service Pack 1
No idea what computer it is because i bought it at ALDI and it doesnt say
3Gb Ram
AMD Athlon 2 X4 620 Processor
1TB HARD Drive
Radeon HD 7770 Graphics CardDid you remember to install the vid card drivers ? ?
As Patio said, did you install the driver?

Did you also attach a power cable to the video card? (see picture below)

Is the fan on the card working?

KEEP in mind it is entirely possible that the card is just faulty. If possible, try it in another computer.Yes, I did install the driver, I attached the power cable and the fan is working.

I managed to get the computer to turn on but now I cant really turn it off :/
It turns on when waking up from sleep mode so this could be a temporary solution. I'm thinking if I completely reinstalled windows it may work if the graphics card isn't faulty?