Somebody School Me On Codecs Please

I have been having DVD playback issues on a laptop as chronicled in this thread:

http://forums.majorgeeks.com/showthread.php?t=125358

Before I start fiddling with codecs, I want to understand them. My understanding is that codecs are needed to play a variety of sound and video types, including DVD's. Any computer might have any given number of codecs installed. These can be installed by default through an OS or by installation of third party software. Some codecs play multiple file formats, while others are more specific. As a result, they may conflict and cause problems. So, here are my questions:

1. Which are default XP codecs?
2. How do I remove some or all of the codecs?
3. Is there a jack of all trades for codec programs?
4. If so, what is the best?
5. If not, which combination is best?

Thanks in advance.

 

I did - but merely explains which codecs do what. It assumes a current level of knowledge of codecs. It does not state "dvd" anywhere in text. Microsoft had a "DV" decoder, but I have no idea what that is. And why are there separate codecs for XP and Mediaplayer?

Which one is responsible for DVD's? And is there a better one other than the MS one? For instance, the one suggested in my linked post?

Thanks for the help!