DVD Player does not start

I recently got a Dell Dimension desktop (don't even know the specifics of the model, but made in summer of 1999). It has Windows 98, second edition. Everything works fine, except when I try to start CineMaster DVD Player. I first get a window saying it is loading, but then immediately after a message comes up: Another application is preventing DVD playback. This happens regardles of how I launch it, directly from a DVD or start application only. I tried starting the computer in Diagnostic mode and Safe mode with same results. Does anyone have a clue what I might do? I have none of the original CDs that came with the computer.

Thanks a lot in advance.

Ted