for further notice, sulfnbk is windows virtual extension driver (vxd) that controls how long filename entries are written in disk file allocation table and master boot record. if that vxd fails, due to some reason, long filename entries would be disabled and your operating system would be down.

example : the folder "my documents" would have a new name that is created by simple dos rules - "MYDOCU~1"

p.s if event described above happened to somebody, and if that sulfnbk is not corrupted, that's because somebody ignited dos application that handles fat entries (for example microsoft defrag from dos 6.2 - if you execute this program from windows 95 and above, all the files that were moved from their original locations to new locations on disk sectors (that's how defragging works) will have dos 8 bytes long filename format and they will lose their original long filename entries (up to 255 bytes per file or folder name))