ATI Radeon x600 pro pci express - install causes infinite reboot loop

[megamawax]

I have a soltek 915g pro motherboard, 2.93 ghz celeron d processor, 512 mb ram. Windows XP SP2. I recently purchased an ATI Radeon x600 pro pci express video card with 256 mb of ram. I uninstalled my onboard videocard drivers and turned off my pc. I installed the new video card, restarted my pc, and disabled my onboard card in bios. As soon as I saved that, my monitor went black. I reset cmos, and enabled palette snoop, and disabled my onboard card again. This time, no black screen, but as soon as windows starts to load the computer restarts and will continuously restart. The only thing I can do is go back and disable the new card in bios and re-enable the onboard card in order to get windows to load. I can't even get to the point of installing drivers for the new card. To get into Windows, I have to disable the new card which means the drivers won't detect the device. If the card is enabled, I can't get into windows, not even in safe mode. I hope someone knows how to fix this. Thanks.