Installed new HDD, IDE, jumper set, cable position OK, yet when I put XP pro disk in CD drive the computer doesn't recognize it, I get DISK BOOT FAILURE. The disc is a valid disk with valid key, I also tried the original disk which was XP home, same result. The same CD drive works fine with other cd's. I question if the Motherboard is compatible with new 400GB HDD vs. old 80GB? The Motherboard is approx. 4yrs old. Is this my problem? I have done this before with no problems, but with different computers. BIOS settings have been tweaked back and forth without any positive results. On boot the computer shows the new HDD and capacity, but I can't get the computer to boot to disk or load disk.