Nvidia 9800 gt preformance edition xlr8 wont boot up

Hi, this is my first post here and it's about a video card.

My dad bought my brother a video card for his computer and the tried to install it but it doesn't work. He says he put the card in the motherboard the when he tried to start the computer, it would only run for 5 seconds before rebooting. It reboots 3 times, and on the third time the computer worked but it didn't detect the video card when I looked for new devices found.

The computer itself has these specs: a 2.00 ghz dual inter cpu, 2 gigs of ram and a 600 wat power supply.

He lost the manual for it and he doesn't know how to properly install it. Can someone please suggest me where I can find a proper installation guide for it or what the problem might be?

I found out that the card is a "enviroment friendly" card (I know it's worse than a regular 9800gt, but my dad didn't consult me before buying the card  ) that doesn't need it's own power supply to be connected. It's a underclocked version of the 9800 and it's suppose to be running on it's own without a seperate power connector powering up the card, but for some reason it refuses to work.

I suspect the powersupply to the problem, but I have no idea how exactly a video card works with the power. I don't have a clue on anything such as volts or amps or if I should adjust anything to make the card work.

Please help, thanks.