there's a program called avicodec
get it here
it will tell you exactly what codec you need and whether or not you have it. It will also usually give you a link to where to get that codec. It's helped me out many a time when I get something compressed with the most out of this world codec.
Also, most codecs install themselves automatically. Just in case though, just put it in the wmp folder.
edit: by the way, where did you find the torrents for the episodes of good eats? I love that show and it would be nice to have them for when I actually want to cook something from it.