Put the HDD
(the actual 3.5" silver/black Hard Disk Drive, not the PC unit) wrapped in about 14 sheets of newspaper within a series of plastic bag (three layers deep) and put it in your freezer for 4 to 8 hours
.When it thaws out the actuators and drive heads will probably start moving freely again.
You shouldn't loose a huge amount of data either.
- Not this is not a joke!
Then use TestDisk to recover your data: http://www.cgsecurity.org/wiki/TestDisk