2 external Maxtor usb drives plugged in when booting I get this message "a disk error has occurred hit ctrl alt del" and the machine a dell xps9100 win 7 64bit will not boot. if I unplug the drives it boots no problem. if I plu either one in I get this message. I tried plugging the drives into my laptop win 7 basic and it boots fine. anyone have a clue why this might happen?