Re: PC freezes upon startup
You took it out and it booted with no problems. It sounds like you never removed the drivers for the onboard video? That sounds like your whole problem.
Uninstall the drivers for your on-board video and the drivers for the video card you've been trying to use. You said you've tried a few different video cards, were they all ATI cards? If not then remove any other video drivers that might be installed. Shut down the PC and install the new video card. Start the PC and enter the bios setup, there maybe an option to disable the on-board video, do so if it is available (some motherboard will automatically disable the on-board if a regular video card is detected). Save and exit the bios. When Windows loads you'll need to re-install the latest video drivers for the card only.