Hes upgrading from a Geforce 7900 GT, and when he turns it on, the computer wont boot. At first i looked at the power supply and it was a 300W, then i grabbed another PSU, which is 450W, and the computer still wont boot. I change the video card and it will boot, but it just wont boot with the 9800.
I don't really get a beep or anything with the 9800, no output at all from the monitor. But when i go back to the old 7900 GT, it will boot just fine.
According to the Extreme Power Supply Calculator ( http://extreme.outervision.com/psucalculatorlite.jsp ) the 9800+ GTX draws 50 extra watts vs the 7900GT. You were right to assume a power supply problem. What model is your 450w power supply? Wattage can be deceiving, with cheap brands hiding the wattage in the wrong rails. Also what is the ampage on the 12v rail?