Well you are pretty screwed I'm afraid. You have two options:
1. You get another identical hard drive, take the controller board off the new hard drive, and try to install it on your old drive and pray that the drive will work again. This requires a good deal of skill and patience, and there is no guarantee that it will work. You need to track down an identical make and model of drive for this to work, so if it is an old drive that may be difficult.
2. You take the drive to a data recovery service. They will dismantle the drive in a clean room and pull the data off the platters using special equipment. Expect to pay a huge fee for a data recovery service though. We're talking several hundred US Dollars at least.
Always remember to backup anything important to another medium. That way if your hard drive does fail, you don't get stuck in this predicament. Data recovery services are very expensive after all, and may not be able to get everything back if the platters are damaged.