I suppose there is the potential to damage your logic board, but that's doubtful. It simply won't let you boot.
A PCI or AGP graphics card sold for use in a Windows PC will not work in a Mac. Some can be made to work with a firmware flash, if you can find one for your video card on the net. Even in that event, a 'flashed' PC vid card will often be unstable on a Mac.
Find a replacement video card that is expressly sold for use in a Mac.