That's what I thought as well. But like I said, when I plugged in the radeon 5750, I still couldn't get a display. I'm not sure if there's a way to test the PCI slot for the card or maybe there's an issue with the power supply? I'm totally clueless.
Edit: When I say pink screen, it was a shade of pink across the screen not an entirely pink screen. I could still see the desktop and icons. I'm not sure if that matters.