Helen, did you use Roots IV prior to moving to UFT?I believe the so-called "X-files" (X_PHBOOK, etc.)were changed to V-files (V_PHBOOK, etc.) with UFT. These are image library files, from what I recall. If you changed computers or moved the files to different directories, you can get that message. You may just need to locate the files on your hard drive and designate where the files are to the program. It might be more than that, however.
If you already haven't, you may want to write down each step you took to get to that point and the exact message. Then get back to someone (you can always e-mail me).