The term for this is "ripping" a DVD. I imagine you're trying to remove the copy protection.
Unfortunately, this is one area where the PC is far better than the Mac. There are 2 Mac programs that will (maybe) do this.
The SEARCH link is your friend!
Here's one thread, if you search you'll find more:
http://213.155.27.24/forums/index.php?show...mp;hl=handbrake