im trying to fix up a tri core custom built AMD Athlon machine by re-installing Windows on it, but my only problem is, when the hard drive is plugged in. I CANT BOOT OFF OF ANYTHING! i can't boot off of a flash drive or a DVD, a blinking underscore just appears, I've tried 3 different hard drives, a SATA drive, and 2 IDE drives, when I boot up with no hard drive. I'm able to successfully startup from an installation disc or USB, but I can't when the hard drive is plugged in. the motherboard is a biostar A880G+. any help?