Well I have been recommending that people do NOT install codec packs .. Many machines may have a conflict because of it.
I Have been following this advice for years and just using a few individual codecs to do the job. Read this .. just one instance of many ..
http://www.howtogeek....y_Codec_Packs_Are_Bad
Codec packs are like throwing in a whole toolbox of spanners to find a couple to undo a nut and bolt.
For DVD playback in ANY DirectShow player (like WMP, Zoom, etc) you need from links here ..
http://www.inmatrix.c...r/formats/mpeg2.shtml
Just install the Gabest MPEG2 splitter, DScaler MPEG2 video codec and AC3 Filter (this will play AC3 and other formats)
The AC3 filter is 800Kb, DScaler Audio/Video 800Kb, and Splitter 400Kb. That's all.
They are not programs .. will not run when un-needed and do not interfere with Windows codec priority, unlike most codec packs.
In addition, If you want DIVX/XVid and .flv playback, you need little more than flv splitter and FFDShow codecs from here
http://www.free-codecs.com/
You just don't need all that crap bunging up Windows!