Sounds like you are jumping the gun since VISTA is not officially out... unless you got hands on RTM or beta version.

Maybe allow software developers to test their products and release new builds that are compatible with VISTA (officially due out Jan 30).
You can narrow it down what codecs in particular you need instead of installing mega codec packs. FFDshow along with Directshow player will play most files. TRy identifying what video/audio codec the video file uses.