The thread is kinda old now but, yeah, I've done it many times. I watched the movie Contact and some other one, and many instructional DVDs from Homespun. It was on XP and it happened exactly as I stated, put in DVD, it launched Windows Media Player and I watched it. Now I understand that sometimes things get munged up and in that case as everyone else in this thread says - get VLC Player. Cheers!
I have Vista (ugh) and WMP has never played a DVD for me.