Asus 4A78T-E

Have been using this motherboard for couple years, with a Single BFG GTS250 Nvidia video card...then the hard drive died...got new harddrive, and reinstalled win7 home premium..had to use onboard video to load win7, windows would not detect the BFG card, so loaded the chipset drivers for the motherboard as well as all the other drivers on the disk from Asus..the BFG still would not work, so installed an ATI video card from a working Dell 980...still will not detect the add-on video cards in either slot...am running a Corsair 850w power supply and have been for well over a year...EVERYTHING seems to work fine in this PC except for the PCI-e slots...any ideas?? I have several years of building computers from scratch, but this one has me puzzled...i have changed the bios around several times from VGA to pci-e and back, still will not recognize the cards...HELP>>!! PC works fine as long as i'm using the on-board video...