I now have exactly the same problem you describe under exactly the same conditions (i.e. reformat and OS upgrade to XP).
Today is Jan 19th. Did you find out what to do?
I guess I backed up using "back it up" two different ways. I don't know how. Program is definitely not intuitive. I WAS able to restore some of what I backed up before I reformated but now cannot. Files I can't get back have different icons and are called folders, not "Nero back-it-up-documents".
Downloaded .pdf manual from Nero.com to get details....same worthless info as in pamphlet that accompanied software.
Please respond to firstname.lastname@example.org
either way. If you didn't find solution and I do, I will let you know.