ATI Radeon graphics card problem–computer won’t start

Hi everyone…I tried contacting Asus’ customer support about this problem, but, well, so far their customer support has been…sub-par. I hope maybe someone here can help me out.

I just bought a new Asus ATI Radeon EAX1950Pro graphics card, and my computer does not start when I have the card installed. The system turns on for about ten seconds or so, nothing appears on the screen, then it shuts off for a few seconds, then does the same thing over again. I upgraded to a 600W power supply thinking that this was the problem, but it still does not work. Everything works just fine when I install my old graphics card. Any ideas?

1.25GB RAM
3.0GHz Pentium 4
600W Cooler Master power supply
Windows XP