You can try a little trick I have used many times, including once this past weekend. SOMETIMES all that goes wrong on an older drive is that slow corrosion by air develops into a bad contact on one or more pins of a connector. So you power down and disconnect the power cord, then open your case. Carefully disconnect the data ribbon cable from your drive, then reconnect it. Do this three or four times. Now do the same at the other end of the cable where it plugs into the mobo. Repeat for the power supply cable at the HDD. When I'm doing this, I usually do this for all my drives at once. Check to be sure you did not loosen anything by mistake, then close up and apply power. If you're lucky, this will have scraped any dirty surfaces on pins and restored the connections, and your drive will be back.
If this does not solve your problem then you probably really do have a bad HDD.