I found a solution to my problem. don't know if it would work for you.
i had a WD passport drive that showed up as unknown USB device, no driveletter and no data recovery software helped either.
as a last attempt I ripped the drive out of the casing and mounted it in a case that I bought at almost no cost, plugged the thing to my computer and it worked. no problems at all.. :-)
i am currently backing up my information to my harddrive JIC.