how do i get rid of a codec that messed up my computer?

I download a show on my computer and when i tried to to play it, it made no sound. so i got a codec for it and it when i tried playing it the video didn’t work. Now my AOL instant messenger makes wierd sounds and I’m not able to use Windows Movie Maker because it closes automatically. I scaned my computer for viruses, and i had none. I can seem to find a way to get rid of it, do any of you know how?

Here is a guide for win2000 if you have xp is almost the same or just use restore system and go back to a date prior to installation of that codec.For restore go start/programs/accessories/system tools/system restore.Click on any day and check and choose the closest checkpoint and restore the system.http://www.jsifaq.com/subh/tip3800/rh3868.htm