keep in mind that while you can use Windows Media Player to play DVD's you still have to have whats known as a DVD Decoder installed or it won't play. If you do have a DVD Decoder already then WMP is pretty good in my opinion. I also use interactual player from time to time (it's the program on most DVD's that have DVD ROM features). Interactual player can be quite buggy at times but is often the only way to see the DVD ROM features on many discs, of course most of these features aren't worth seeing anyway.
If you don't have a DVD Decoder you will have to buy one. There are no free ones that I know of although many companies will let you download a trial version from them that works for 30 days or something like that. You could probally get away with using various free trials for a long time.
Try using Froogle.com or Bizrate and searching for PowerDVD or WINDVD. You can often find vendors selling these programs on CD's that include the Decoder, a program for playing and a DVD creator for making your own DVD's. I believe I saw PowerDVD going for as little as $6.95 once (an old version but still completely usable).
hope this helps.
Jamie
