Doesn't it seem standard that if your PC comes with a DVD player/burner you should be able to watch DVDs on it without spending more $?  Of course!  There IS a way.  Most computers that have a DVD and Windows XP, have Windows Media Player 10, if not, it should be a free download from Microsoft.com.  Windows Media Player 10 will play DVDs, but you need an MPEG 2 codec.  How do I get this?  Go to download.com and get a program called PowerDVD.  The free trial is fine because all we need is the MPEG 2 codec that comes with the program.  Install PowerDVD and you should be able to watch DVDs on your PC with Windows Media Player 10.