i have an LG external and also internal ( in my QS G4 ) burner that can use those DVD-ROM's

Can i install and run system 8.1 from at DVD-ROM in the G4 or my 8500 ?

The 8500/G3 (Sonnet) has FireWire and USB ports. I have used the LG burner with the 8500/G3 to rip/burn DVDmovies but never thought of running a system on a DVD-ROM.