Codec packs are sets of codecs and filters which are used to encode and decode audio and video files.
From personal experience, all the problems I experienced with Windows DVD Maker were caused by codec pack issues. I took the decision to stop using codec packs and installing individual filters and codecs and since then, i've had no problems at all.
Google for the following as they may help:
DivX v6.8.5 (The installer includes the full DivX bundle including player/converter etc but you only need the codec)
ffdshow (Beta 6) Revision 2527 (19-12-2008)
Haali Matroska Splitter v1.9.42.1
XviD v1.2.1 (04-12-2008)
Hope that helps ;)