Hi
There are specialist companies selling replacement hard disk cuircuit boards
(probably cheaper than a new hard drive)
It is best to send your faulty board to them so they can transfere the firmware to the new controller board
otherwise the new board may not work
example
http://www.hdd-parts.com
You seem to have the skill to solder so if you can remove the circuit board from the hard drive without damaging it
go ahead
If the only thing of value on the hard disk is Windows itself it may not be worth it for a oem home version
but a Pro or Ultimate retail version would be worth keeping.
regards
Mike Barnes