I think I should point out that although VirtualBox is a very good virtual machine, it is not a Windows operating system, it merely provides a framework within which another operating system can be run. Which in turn means, the user still needs a Windows license and an install CD. I, for one, do not have that and I do not intend to buy it, either.
I would also like to point out that there are several standards compliant formats for movies/videos which will play under all operating systems, and it should be quite easy for the production company to provide the DVD contents in such a format.
The ZIP file mentioned by Paul would be a great help for all MAC and Linux users, and the approach to run the contents via a browser may work well (although I'd have to have the zip file to test this). Another possible alternative would be to provide the DVD contents as an ISO image file, which can then be used to burn a DVD from it, and that DVD should play on pretty much all standard DVD players.