Hi there zhimomi,
That is really unpleasant.
Is the HDD even spinning up?
My suggestion would be to try using a different cable and attach the drive to another computer.
In case the issue persists, then there is something wrong with the enclosure or the HDD itself. I believe it is not recognized by Disk Management right? In that case, your safest bet would be to contact a data recovery company. It will not hurt to contact the manufacturer's Support as well.
Apart from that, you can:
- Even though your HDD won't be picked up by a data recovery tool, you can use one:
http://www.tomshardware.co.uk/forum/id-1644496/lost-data-recovery.html
- RMA the drive in case it is under warranty. You will not get your data though.
- Some users take the drive out in similar cases, in order to attach it internally. Keep in mind that this may not work. Also, if you decide to go with a data recovery company, just unplug the drive.
Cheers,
D_Know_WD