If you think the problem is related to the drop, then the chances are; its probably the HDD which is damaged. I mean it makes sense too if its producing squealing noise indicating you've probably damaged the bearing which keeps the hard-disk spinning.

I will strongly advice you backup your important stuffs NOW as there's no way of telling when it will stop completely (data recovery is more costly then you could ever imagine).

After you backup your stuffs, download and use HDDScan: http://hddscan.com/

Just keep your finger crossed that S.M.A.R.T doesn't tell you that your Hard-disk is about to die. If it does, the easy fix will be replace your HDD (but we will then had to worry about Operating System later).

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