If the HDD hasn't failed but you still can't boot to it, you may be able to use one of
these little guys and slave it into a desktop.
I just had one of our users' laptops do that and it just did not want to play. Tried to re-install Windows over the old installation but it would only work if I formatted the drive. Using one of these adapters, I was able to slave it up and get all the data the guy needed.
If the drive has failed phisically, then, chances are you can still have the data recovered by OnTrack or another such company which actually disassembles the drive and mounts the platters to a different location so the data can be extracted. Definitely the MORE expensive way to go.
Randy