I am having trouble getting windows 7 loaded on my ASUS P9X79. I get to the set up screen for win 7 but then it says "A required CD/DVD drive device is missing. If you have a driver floppy disk, CD, DVD, or USB flash drive, please insert it now." I do not have a CD drive right now but i should not have to have one if i have the boot disk mounted on my USB.... HELP ME PLZ!!!!