What are you trying to do? Play 2 DVDs at the same time? If u have 2 drives in your computer...say D and E BOTH are CD drives, and you're trying to play both? If u're trying to do that then the other ROM drive must be just a ROM drive, not a DVD-ROM drive. Or, if you're asking why does ONE DVD plays in the drive, and u take that out from dirve D and put another DVD in it and says no DVD in the drive, then its not the software or the hardware, its the DVD's fault. whether it was not burned proplerly or it could be corrupted. i believe that happens to some nepali Movie DVD and some Indian Movie DVDs. im not sure what you was asking, i answered what i figured.