External HDD unreadable after scandisk

Hi,
I have a WD 320 gb elements external HDD and after having issues with nortons ghost and reading a post suggesting running scandisk I did this for both my C drive and the external (by right clicking on the drive in my computer choosing tools then error checking and choosing the opts to both automatically fix file system and scan for and attempt recovery of bad sectors). Because of this it seems its become unreadable and unrecognised by windows.

It took hours to run this check I just let it go but I estimate 6 or 7 hours all up. It rebooted when done so I didnt see any messages and it was set to run scandisk on C drive when done so it was this morning (after running it overnight) I discovered that the external drive was no longer being read.

I took it out of the cover and plugged it direct into the motherboard and windows does attempt to recognise the hardware as some kind of CD drive but it does not show under disk management.

A reboot with the drive connected causes windows to crash.

I have tried it on the laptop too........ no luck!!
Any ideas? I would be most grateful for any suggestions