Are you seeing any error messages when you try to play files in WMP?

Might be a codec problem...try downloading some codecs & see whether that helps. Have a look at the thread below - it has links to various codec packs (the K-Lite & XP Codec Packs are popular & also the Vista Codec Package).
Or, if you like, you could try VLC Player. It's free & has codecs installed to play most file types. It's a good player The thread below also has a link to download VLC.
http://www.gnutellaforums.com/tips-t...p3-fixers.html