Windows 7: Iomega external hard drive won't show up.

I have a 1 Tb Iomega external hard drive that suddenly stopped working for no apparent reason.
It worked fine for a long time, and then one day it didn't show up when I plugged it in, and haven't worked since.
Been looking around the internet for a solution, but haven't really got any wiser.
There's no icon in the bottom of the screen when I plug it in, and it doesn't appear in disk manager either.
I've tried all the USB ports on my computer (HP pavillion g6). The disk has an external power supply, and the LED on the disk is glowing, so I assume the problem is somewhere in the computer.