Hi Yoden,
Welcome to Windows Vista Answers Forums!
Another user had similar issue, please refer the following link and try the suggestions to see if it will fix your issue:
http://social.answers.microsoft.com/Forums/en-US/vistamedia/thread/c42b0e61-ce50-4853-8952-64a2b83c3601
If you have any third party codec package installed remove that and check with Vista Codec Package.
You may also refer the following links to get more information:
Troubleshoot problems with creating a DVD-Video using Windows DVD Maker
http://windowshelp.microsoft.com/Windows/en-US/Help/bc732dc8-0cde-43fe-bec6-cd85215810801033.mspx
DVD-Video burning: frequently asked questions
http://windowshelp.microsoft.com/Windows/en-US/Help/f605df6c-0dfe-4f6c-b8e2-866d8cb362251033.mspx#ER
Hope this information is helpful.
Praseetha K
Microsoft Answers Support Engineer
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