Dual plextor drive confusion

[gauss67]

I built a computer for my uncle who runs a karaoke business. I installed 2 Plextor PX-716A drives and he is running Microstudio 6.10. When creating a custom assembly disc, he gets confused with the the 'Reading Drive' and 'Writing Drive' selection because it doesn't list the drive letters. Is it possible to display the drive letters in these boxes? Or is this issue corrected with version 6.11 or 6.12? The only other way I can think of fixing this problem is to have a different firmware version on each drive, however I would prefer not to go down that road.