The problem was with the codecs the DVD players were using.

When I installed Windows XP I got with the CD the Windows Media Player Version 8. I intalled Windows Media Player Version 10 with no success. However I noticed that you can add software plugins to the player. I've installed what looks like a recent plugin from Nvidia (the graphics card I am using is Nvidia GE-6600) and that sorted the problem. However I have used a 30-day trial version so the solution will cost a little money.

The Cyberlink DVD suite (30 day version) was in the supporting CD that came with the Plextor DVD drive I bought. I decided to purchase the latest Cyberlink DVD Suite which actually plays pictures and sound.

The impression I am getting is that although the hardware may be first class from reputable manufacturers the supporting CD may have bundled software that may be out of date. Is this opinion fair?

Anyway thanks for your suggestions.

The speakers came with the monitor I bought (Compaq FP 1706). I attached the speaker plug to a rear !!!!og speaker socket (the green one). I've disabled "Enabled digital CD audio for this CD-ROM device" option for my DVD drive.

Your idea about using the right codex turns out to be the cause of the problem. I don't know whether the codecs are third party. I only used the software that came with the DVD drive. Where Plextor got the software from I do not know.

Once again thanks for your help.

Stepniac