I know Veritas Backup Exec 98...or whatever it's called now, will do this. I also think Drive Image and/or Ghost have a version (Pro?) that will span. I use Plextor CD-ResQ to span to cd-r/rw which, I believe, only works with Plex burners, but is based on Ghost....even shows Symantec in the copywrite. I've used Backup Exec since '96, spanning tapes and cd-rw's. Very nice to have a floppy emergency restore.....you don't even have to reinstall the OS or backup program....it will reinstall everything.
--Randy