I have a 7900GT. I also have a problem. My computer starts up for a few seconds, does a boot check and shuts off. The different parts make noise in a pattern and stop at my video card. I know that sounds wierd but its the only way I can explain it. Once it gets to my video card its off. Ive tried changing the psu connector and dusting it off. If you can think of anything else to check thanks in advance. Its also plugged in.
Is it plugged directly into a 6 pin PCI-e power connector on the power supply, or is it plugged into the supplied adaptor that came with the 7900GT?
If you are using the adaptor that has the 6 pin plug on one side and two 4 pin molex on the other, make sure to use both molex connectors not just one, and make sure they are plugged into regular molex feeds, not the ones marked "fan only"
The picture that Pauldh posted, the plug for that plugs into the 7900gt on one side, then branches off into 2 more. Both of the branch offs connect to PSU connectors. Both have 3 spike things that plug in. That means they do the plugging into. The PSU connectors do the getting plugged. So thats 6 total spikes. If that helped at all, then good. I also noticed I didnt take the wrapper off the fan area. The thing is I beat FEAR and Prey on it before I got problems, and with the problems I made so far, i'm supprised it still starts up, well it used to, but it does technicly start. Just dosent go for to long.