This drive does not appear on my desktop anymore. Neither in Disk Utilites...

Make sure the lead/s that attach to your hard drive are securely seated
if your computer came with a motherboard disc the drivers could be on it

click start control panel administration tools computer management device manager look through all of your devices if you see a yellow question mark?or exclamation mark ! or red x
right click to reinstall drivers or

if you can see your usb but its not working
ports(com&lpt)right click update driver
hope this helps

click start control panel administration tools computer management device manager look through all of your devices if you see a yellow question mark?or exclamation mark ! or red x
right click to reinstall drivers or

if you can see your usb but its not working
ports(com&lpt)right click update driver

sometimes the wires inside the cable will be damaged due to bending or stretching or placing heavy equipment upon the cable

just replace the cable of the hard disk, when you plugged the external disk drive you got that windows could recognize the USB device change the cable everything should work fine again,

check the USB leads that attach to the motherboard usually red-white-green-black make sure they are securely seated and have no dust build up on them dust will cause static and a lot of unforeseen problems

if this fails to fix the problem
you might have to install a usb 2 or 3 card they are cheap and easy to install you can buy these on Ebay very cheap
hope this helps

Welcome to Fixya.

If your computer does not recognize the hard drive, here are few fixes you may want to try:

• Disconnect the hard drive and reboot the computer. Reconnect the hard drive.
  
• Connect the hard drive via the USB port on the back of your computer.
  
• Use a different cable or if this has a firewire interface, use the firewire if you have a firewire port. If this works, then the USB connection is failing.
  
• If the drive has been formatted, please make sure that it was formatted correctly. Refer to your user manual.
• Try connecting the hard drive to another computer and see if the recognizes it. This will let us know if the original computer has a USB port problem.