This is a very common issue and a pin in the neck for users and video producers.
WM Player is not an authorised DVD player, Microsft specifically says so in there user manual.
The trouble with many Windows installations are that the file associations are set for WM Player to play every kind of media which is stupid
The DVD drive for each PC will have a dedicated DVD player installed for this specific purpose, you should use that, examples are; Roxio Media Player - Sonic - Cyberlink Power DVD
On all our DVD case wrappers we have a warning notice that users should only use the correct player and to clode down WM Player if it launches.
Some DVD duplication houses said it might help if I author the DVD on PC hardware. Any thoughts?
Yes, dont use suppliers who dont know what there talking about.