A. The requirements for DVD decoder (MPEG 2 decoder) integration with Windows Media Player (WMP) can be complex, so Microsoft released the "Windows XP Video Decoder Checkup Utility," which you can download at http://www.microsoft.com/downloads/details.aspx?FamilyID=de1491ac-0ab6-4990-943d-627e6ade9fcb&displaylang=en . The utility lets you view installed decoders and their compatibility and set the preferred decoder for the system.
After you download the tool, execute the file and follow the onscreen instructions to install the utility. Once installed, start the utility by clicking the shortcut "Windows XP Video Decoder Checkup Utility," which you'll find in the Windows Media group in the Programs Start menu group.
You can view the decoder status and set the best decoder for the system as the default by selecting it and clicking "Set as Preferred," as the figure shows. This setting changes the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Media Center\Service\Video\PreferredMPEG2VideoDecoder value.