Just to add, if nothing of the above works
Just to add, if nothing of the above works it is most probably a hardware issue with the cable that connects the internal HD to the Motherboard.
If you have guarantee on your product, head to the apple store, if not, go to ifixit.com, get the cable, and replace it for the old one, you will find further instructions in the same site´s product review.
MacBook Pro, Mac OS X (10.7.3)