Software to....

[Helltech]

backup an unusable HDD. I don't know what happened to my external, probably disconnecting it without having the computer off. But I have ruined it so hardcore that when I plug it in it says "windows must format (instert drive letter here), before it can use it." I have a LOT of important stuff on there, what software can I use to get files off it? I know they do it when you take it in to a shop, but they charge like 100 dollars to do so.

[caperjack]

now you know why they charge the 100$, chances are if your computer cant read the drive ,no software out there is going to help you back it up, try removing it from the case and putting it into a computer tower[as a slave if it ide ] and see if you can access file that way

[Jupiter 2]

This happens often. There is nothing wrong with the HDD.
Unplug the drive, from the usb port. Turn on the computer. After load up and the hourglass is back to pointer, plug in the hdd usb cable (A Hdd usually requires an external power supply too unless it is a laptop hdd). Windows will show that a new device has been found. It should be okay now.
Sometimes plugging in before you start can confuse the startup processes.
Otherwise try this - The External Drive may be set to Master. Set it to Slave. Jumper settings shoud be on a label on the drive.
Also, in BIOS, set all drives to Auto (select). and there might be an option for Usb2.0 and Usb 1.1 , enable both. Also Boot option may be set to other, set this to None so that the sequence is either
CD/Hdd-0/Floppy/None or Floppy/hdd-0/CD/None. Save and exit.