Don't put the hdd in an oven or anything... that's bull. A harddisk spins around 7200 RPM , and a 75 mph wind inside the unit causes the head to float... they normally go bad due to the head crashing , etc.
Seriously try the harddrive on another computer , and if it is a BIG harddrive ( physically about the size of a VHS cassette tape ) , take the harddisk out of it's enclosure ( pretty much a container ) , connect it via SATA or IDE connection on a desktop computer unit , and see if it shows up then , connect the power cable.. and see if it shows.
Put your ear up to the harddrive while it is making a constant humming sound , and not making any loud CLICKS or scratching sounds. Possibly the IDE/SATA to USB controller inside of the unit may have failed... so try what I said and see what it does.
If you don't hear a pinging sound when you plug the harddisk in ( Windows telling you it's in ) , and it doesn't show anything on the bottom right hand corner about a device being plugged in ... it's most likely the IDE/SATA to USB adapter. External harddrives by default are initialized by the manufacturer... so I'd rule that out of the equation.
Then again ... what brand of external harddisk is it ?... because if it requires an AC Adapter... maybe that possibly failed because most external units ( unless based upon laptop harddrives ) require some form of external power source to run... the 5 volts supplied by a common USB cable isn't enough power to run a typical desktop style hdd
John Electrical Engineer/OSHA500 Certified Safety Trainer
August 2008