hi john
external hard drives are one of the most fragile when it comes to data protection and there are more and more instances were people are losing the use of their external drives because of power outages or accidents
however you have several methods of retreiving the data from the drive and these include :
1. attach the drive internally to your pc and in the case of a ide drive you need to set the jumper to "slave" and then attach using a master/slave ide cable ,however sata drives use channels and can be connected using a sata data cable to any existing sata port...then with both methods windows will recognize a new peice of hardware and will install the nessecary drivers ect........then simply move or copy the files from the rescued drive
2. next you could buy a new external hard drive caddy,these cost around £15 and will simply create a new external hard drive which then connects to any spare usb port,however you can also buy e-sata based drive caddys which have faster data transfer speeds
3. you can buy a emergency usb to ide transfer cable,this connects to your rescued hard drive and then into a usb port,then data can be moved or copied from the drive to a pre-assigned folder on your pc,however they dont make these for sata drives
the above methods are ok for external drives were its the unit is at fault however if the actual hard drive has become damaged or faulty then they wont work,you then have no option but to contact expert data retrivial companys who charge quite alot of money to save data from damaged hard drives
they charge around £200 however the process involves removing the drive platter(disk) and using a special tool finding and transfering the data to removable media
note : aswell as device manager you should also use drive management in "administrive tools"..this will show all drives currently attached to your pc and this also includes unallocated space aswell
any problems let me know
good luck john !