Need Help with Video Codecs

[Koyanisquatsi]

Not sure if this is the right forum. Somehow my video codecs are seriously jacked up. I'm using wmp10 xp sp2. The svcd's play with a black box outline and the xvids aren't in synch with audio. I've tried removing thru add/remove and then reinstalling. I think I screwed stuff up by installing a codec pack. How can I completely remove my codecs and then exactly which ones should I install and in what order?