Earlier today, I swapped out my GTX 670 for a friend's GT240 (he wants to try the card out before buying it from me). I played a few games of Company of Heroes 2 and a bit of Skyrim, then had a wonderful notion that my computer needed a good 'ol cleaning. I ran CCleaner, Defraggler and Guru3D driver remover. During that final step, I accidentally removed all drivers for my system. I have attempted to reinstall my GPU's drivers, but the card is no longer even detected. I have tested every component along the line, even trying other PCI ports and DVI/HDMI cables. If I take out the GPU, the system runs fine, with video handled by integrated HD4000. If I plug the card in, everything goes black. I've tried F8ing to safe mode--I really don't know what else I can do. Help. Please.