External hard drive won't mount
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Try replugging the cables and connections first before concluding that it has failed.

There are 3 main possibilities if your external drive won't mount:

1 is that the logical structure of the drive is damaged. The good news is that this can often be fixed with software, and although some files may be lost, there is a good chance of recovering most of them.

2 is that the enclosure (powersupply or bridge board or cable connections) is bad. In that case you are in luck because if you remove the drive mechanism from the case, and put it in a different external USB case, it will work.
(this will however void the manufacturer's warranty)

3 is that the drive mechanism itself has failed. In that case you may be up a creek. If the motor isn't spinning the drive, or if the drive's controller board has burned out, then nothing short of repair by an expert is going to help. Data recovery firms will fix it, but for a fee of $400 - $ several thousand.

If your problem is logical (#1)
-- that is the drive spins properly and shows up on the USB bus but there are no accessible partitions or data --
then you may be able to recover data from it, or repair the logical damage. Programs like SpinRite from GRC labs and Ontrack utilities might repair the damage, programs like DataRescue PC, Pandora and others might recover data even if the directories and file structure are damaged.

SpinRite http://www.grc.com/spinrite.htm
Diskinternals Partition Recovery http://www.diskinternals.com/products.sh…
OnTrack software http://www.ontrackdatarecovery.com/file-…
Pandora Recovery http://www.pandorarecovery.com/
DataRescue PC http://www.prosofteng.com/products/data_…
Recovery Review - list of recovery software http://recovery-review.com/
Recuva (free) http://www.piriform.com/recuva

Article on recovery http://en.wikipedia.org/wiki/Data_recove…

There are some websites that have tools you can try, and then if it looks like it can recover some data, you have to pay to do the recovery

VirtualLab http://www.binarybiz.com/

If all else fails, you can send your drive to a data recovery service, it will cost hundreds or thousands of dollars depending on what the problem is.
If you are going to send it out for recovery, the less fooling around with software you do with the drive on your own, the better.

DriveSavers http://www.drivesavers.com/
ActionFront http://www.actionfront.com/
TotalRecall http://www.totalrecall.com/

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