Dead USB external HDD. Disk spins, light is on, but no one is home.

I have a HDDR250E03X 250GB external USB powered harddrive. I used it just yesterday without a problem on my computer and only a few days ago on a friends computer without problems. Now I left my laptop on overnight with the external harddrive attached and fell asleep. I woke up this morning and the harddrive icon is gone. The computer doesn't see it. The bios doesn't see it. I figured it might be the heat sensor but cooling it down a little nor heating it up seemed to help. Mind I didn't do either in any exstreme. I tried it on my friends computer and still nothing. The disk spins, the light on the external goes on, and all works as it should but the computer won't read it. I run windows vista, but I have tried it on a windows xp system as well. I honestly don't care about the harddrive, it's covered under warrenty, but the data on it is not. I need to get some important files off it pronto. If you have any suggestions it would be much appreciated.