How to Check if DVD Decoder Software is Installed
By default, Windows XP does not come with compatible DVD decoder software installed. To confirm if you have Windows XP-compatible DVD decoder software on your system:
Select Start > Run
Enter cmd in the Open box, and click OK
Type dvdupgrd /detect and press Enter
A Windows dialog box will open with identifying information about the installed software. If No decoders found is displayed, no decoder is installed
You can purchase Windows DVD decoder software from 3rd party software companies listed on the Windows Media Web site for less than $15.
http://www.microsoft.com/windows/win.../buypacks.aspx