I use a program called Gspot to get this information. I find it has alot more info then the AviCodec program. If anyone wants to check it out you can grab it from
http://www.headbands.com/gspot/ one thing I would also like to add is that installing codec packs (like the Nimo codec pack) can do more harm then good. It's always recommended that you use a program like avicodec or G-Spot to identify what codec is needed by a video and download and install that codec only.