OK, sorry I haven't replied to this - been having a bit of server trouble! Let me recap:
1. Neither drive will play a CD through the headphones. Not even normal, bog standard audio CDs with no enhanced content.
2. The CD with DVD Rom Material included, will not play the audio tracks, only the video content, through Quicktime. There is no Audio menu, and upon opening the files, no audio files are shown.
3. I have unticked the Digital Playback box in both Properties of both drives, which has had no effect on the problem.
I was wondering if it could be something to do with XP not having a dedicated CD Player, other than WMP? When I had Win98, it had it's own CD player, and you didn't need third party software to play music CDs. The headphones worked with Win98, but not with XP.