Windows media player

I was reading the site about codecs and downloaded a program(cant remember what it was called) which had ALL the codecs to date .When i installed it i couldnt even open applications.Now when i try and play my MP3's on wmp8 it says that the audio codec is not installed on this system. I have downloaded the codec program from microsoft and it still would play mp3's. How can i uninstall and reinstall wmp using the XP installation disc. Or would it be easier to upgrade to the wmp 9 version.