new video card problems

I have a P4 2.4Gz running Mandriva 2006, and now it's really having issues with a new video card (geforce mx 4000 pci). I can't even get linux to load. It starts going through the loading screens, but then the whole computer power resets after a certain time. Any ideas? It will still boot up with the onboard video if I plug the monitor back into that, so I know it's the new video card that is causing the problem. My PS is barely good enough for this card, so I was wondering if it's causing the PS to trip when a certain demand is placed on it from the new card. It works with windows without tripping offline, but I can't even get into linux to make it work.