There are two simple solutions that will tell you the codecs used, but not how many channels the audio is.
1) In Windows Explorer (XP at least), you can actually choose a column header "Codecs". The defaults are Name, Date Modified, but if you right click on the window's columns you can find many other options. Once you chose codecs, Windows Explorer will go through the files and tell you what the video, audio and subtitle codecs are.
2) If you don't have XP (the above doesn't seem to work in Vista), and you have imported the files into MC, you can use standard views "compression" column. Once the column appears, select the files, right click and go to library tools> update library from tags.
Solution 2 doesn't always work, and solution 1 depends on your OS. Hmmm... I'll be checking out the program jsimo01 recommended too.
