SImpletech 500GB External USB Hard Disk not working

please go to my computer, right click -> 'manage' -> disk management

do you see the external HDD listed there?

windows7
click start control panel administrive 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
if your computer came with a motherboard disk the drivers could be on it
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 also make sure the computers Ram and Cmos battery are securely seated
hope this helps:

To start if there is an AC adapter I would check it's working. This is very easy if you use a multimeter. If it is working, you should then check the disk manager if you're using windows. To do this hit Start, Run, "compmgmt.msc". There you will see a title on the left "Disk Management", click it and see if your hard drive is listed there, then report back.

If it still has a valid warranty, exercise the warranty to get a free replacement.

Otherwise, open the enclosure, and separate the disk-drive from the USB-to-disk-drive adapter, and connect the disk-drive as a 'slave' disk-drive in a desktop computer, to see if the adapter was the problem.

Check the partition size in Disk Management (if running Win7 - download a free Partition Manager if not) and see if the system is seeing the partition correctly. Seagate has recovery software available on their website but you may just have to repartition and reformat.

Sorry but it probably is, go to windows explorer, right click my computer, go to manage and then look on disk management. If the disk does not appea there you are pretty much screwed.
I managed to get the cover up to plug it in to my sata port directly, and it still did not work.

I have found a driver page of simpletech:
http://www.simpletech.com/support/support_downloads.php
I believe that driver for your model is not available in the above link.
The drive would not be recognized when it is not compatible with your notebook hard disk.
I suggest you to contact simpletech for getting the drivers as they will have the hard disk drivers.

Right click on MY COMPUTER and select MANAGE.

Go to DEVICE MANAGER and expand the DISK DRIVES category on the right side window.

You should see the Simpletech drive listed under there. Delete the Simpletech drive and click on OK. Restart the computer.

Windows should re-detect the simpletech and re-install the built in drivers automatically.

This is because your bios is only configured to recognise up to 250Gb. what you need to do is download the latest bios updates for you mboard, install them on windows. then you shoud have no further problems with the HDD.

formatting it to ntfs should do the job