What has probably happened, is that with the fall, one or more of the drive heads have folded over on themselves. Attempting to use the drive will only cause more platter damage.
Your data is LOST unless you go to an expensive data recovery service where they dismantle the drive in a clean environment and use specialist workbench to get the data off. But there are also no guarantees PLUS they might find stuff you dont want them to.
Best bet is to give up. So now youve got a drive with no value. OK. So now dismantle it. Steps:
1./ Create a clean as possible environment. Vacuum and wipe down all surfaces.
2./ Open up the drive case careful
3./ Dont unscrew any screws that mount the platter spindle or the heads.
4./ Look carefully at the arms/heads
5./ Is something folded over? Great if so... thats your problem... but no guarantees you can fix it
6./ If folded, get a needle, toothpick, or something to flip the head back over. Careful NOT to touch the platters. BUt also try counterrotating the platters while you hold the head to help it flip back over.
7./ If there are no flipped heads, can you see other damage?
8./ Attach the drive to an EXTERNAL USB or eSATA box.
9/ Start the PC without the damaged HDD attached
10./ Once PC is logged on, power up the HDD but without USB/eSATA connection
11./ Is it spinning up or out?
12./ If not spinning, "help it start"
13./ Once spinning, connect to the USB/eSATA port
14./ Does windows recognise it as a drive
15./ Good luck
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TIPS:
A. Whatever happens DONT attached the HDD to onboard IDE/SATA controlled for POST routine initialisation. It will fail.
B. If you dont have eSATA, you may be able to hot connect the drive to an internal SATA port AFTER the PC has booted into Windows
C. DONT follow wizzards advance of hitting the HDD. This solution is NOT for a dropped drive, but for a drive that just isnt starting or hasnt been used for a long time. It is used for a "stuck" drive. In your situation, it will only make the folded heads situation worse, and possible introduce yet more damage.