Windows XP was running scan disc on my external hard drive. However it was interrupted by a power outage. Now Windows is not detecting the external hard drive. I tried it on another PC and it is also not being detected. What should I do?
Go here: http://www.cgsecurity.org/wiki/TestDisk
and download a free utility called TestDisk (I downloaded the latest NON-beta version). It's a zipped file, just extract all files to a folder of your choice leaving the option "Use folder names" checked. Then, go to the folder where you unzipped the files, go to the Win folder, and run the testdisk-win.exe file. It runs in a DOS window, even though it says it's a Windows app, but it doesn't really matter at all.
So, start the app (you must run it with administrator privileges), wait for it to recognise all the drives, it will take 5-15 seconds. Choose the external drive. Confirm Intel/PC partition. Analyse it. Proceed. Enter to continue. Write on the next menu. Confirm. Quit the app. Disconnect USB cable from the device following the safe hardware removal procedure. Reboot your pc. Re-connect the device and it should be properly recognised, and the whole thing doesn't take longer than a couple of seconds!
If you are compentent I would recommend opening up the external hard drive caddy, removing the drive itself and plugging it in your PC internally. This will let you see if the drive itself is working or not. If it doesnt show up at all in windows this way, then chances are the drive itself has died. If it DOES work then it is very likely that the USB hardware in the external hard drive caddy has failed, or the power supply has failed.
I would not recommend opening up the hard drive caddy if it is still under warranty.