a case you put a drive into yourself, or one of those WD "Books" or similar from other maker with a drive already in it? If the latter, did you reload the software which allows access to that drive after "going back"?
I installed Roxio GoBack in my Windows 7 OS computer, and a file was installed in my external hard drive during the process. My computer continued to run fine until I attempted to restart it. Windows would not start. I used System Repair, and nothing changed. I then used System Restore to remove Roxio GoBack from my computer. The computer was finally able to restart, however none of my computers can see the external drive anymore, and I am unable to assign a drive letter to it (the option is greyed out). I was able to copy my personal files from it with data recovery software, but I would like to be able to use my external hard drive again.