Perhaps iTunes has become the new audio default player. How to change it back to WMP: Setting default audio program. Almost 'all' windows programs are greedy to become the default audio player which means it opens when you click any audio file. So I suspect this might have happened, changed default without you realising.

* If you are using LW 5.0 Beta & you have it set in LW's options for iTunes to auto import songs, then the songs will automatically be 'added' to iTunes music library once the songs have finished downloading. This is a new change introduced in LW 5 for Windows users, previously only available to Mac OSX users.

BTW since WMP is simply a playlist player, you can still add those songs to WMP's playlists. Just open them up with WMP should do the trick afaik. I haven't used WMP in ages so cannot remember.