Hello.
I'm a Mandrake 9.1 user, and I just recently started watching DVDs on my Sony laptop running Mandrake.
It will work just fine, however, it's not standard with the distro. This has to do with allegations that the DCSS code is somehow a "pirating" enabler.
To that, I give a profound: whatever. If *watching* DVDs is pirating (ooh! I let my EYES download the data! Bad me!), then I'm a pirate. Arrgh, matey. Shiver me timbers.
If you follow the instructions at the website referenced below, you'll be up and running in short order:
http://www.linux-sxs.org/multimedia/dvdplay.html