Are they on the same channel?
Is it only that disk - can they read data disks, cds, regular dvds?
Sorry, I don't know what the channel is,,, Regular music CDs and other DVDs will play. I called Pioneer and they said shouldn't be the DVD hardware but a conflict with the software installed. They recommended I review the task manager in both safe and regular mode.....urgh...Thanks
If the Pata is PATA (parallel ATA) that's IDE. You have 2 IDE devices per channel (connection on the motherboard, and the cable has 2 connectors on it). If they are set up on the same connector, 1 has to be set as slave, the other as master, via jumpers on the drive.
If that's done correctly, then I would pull one, see if one works by itself, then reverse the process. If it works correctly with single drives, and not with dual drives (with jumpers set correctly) then you have at least isolated the problem, could be something to work with the vendor on.