Assuming it's a DVD you own and you're using it within the copyright restrictions, then the short answer is it's dead easy if you use a Mac - for example, HandBrake will let you do it with about 3 button presses.
If you use MpegStreamclip with the right plugins, you can do it on the PC, but you'll need an Mpeg2 plugin IIRC to read the DVD stream, and for that you need to buy Quicktime and pay for the plugin... There must be an easier way, but I've never found it. All I do is shut down the PC and use the Mac instead. In fact that goes for most things to be fair :dance: