I can only suggest that the file structure is different between XP and 7 (one is FAT32 and the other NTFS, eg).

I have had to restore TL files on occasion, but that was the same computer and OS.

The program to open the files is TurboLister. A silly question probably, but are you attempting to restore from within TL, using the specific function? That is the way to do it, not through the file itself.