[Steven Simpson] “I need some way of making it load the default DVD player.”
That’s just the problem…many if not most PCs don’t have a software DVD player, unless they came with a DVD burner and assorted software goodies, or these were installed later by the user- and if they do, it’s a different player on different systems.
DVD-Video isn’t a file type, but a folder containing all the parts, so there’s no default application for the file type of course. This might be possible using InterActual player, but that installs files on the user’s system (usually that doesn’t make people happy). You may want to look into that (there may be licensing fees required).