Are they 2.5 inch or 3.5 inch external drives? Like the 2.5" laptop style drive, the 3.5" desktop style drive inside the external case requires 5 volts DC which is provided through the USB port. The 3.5" drive also requires 12 volts DC power for the drive, which it will generally need to get externally. If they are 3.5" drive I would check their separate 12 VDC power supply.


They are 3.5 drives and I am a moron. I hadn't noticed the power cord had become unplugged in the rat's nest of cables behind my computer. (I only had one hooked up to my computer at the time due to my 2006 model PC's limited amount of USB ports.) I've got so many cables back there I hadn't even noticed that one was not plugged into anything. I have no idea how I unplugged it.