Hi, i spent a good few hours trying to sort out the usb device not recognized problem, and none of the all over the forum fixed worked for me, as all trace of the device just disapeared.
This worked for for iomega 500gb external, gave it a go because my warranty seals were already broken.
So yea, tried all the sensible options, replugging everything, device managering like a mother-bit ch, my computer . management etc.
So then i took out all the casing screws to give it a look. If you do this, i fond that pulling out the usb adapter card on the inside leaves you with, in my case, a nice internal sata drive, which when put in internally, works totally fine.
Yea, you no onger have the externalosity, but at least you have all your data...and dont have to take a shit load of copywritten/confidential material to a shop for a fix.
Hope this helps someone
Ric