hi...open wmp11, on the top where the classic menu is select play>shuffle.
if you can't see the "classic menu"...rt. click on the top bar of the player...view>classic menu
or just rt. click on the top bar of player(by where the back and forward arrows are).....play>shuffle
you can also do it from the individual playlists if you have some...now playing>show list pane...next to the name of the playlist on the right there's a drop down menu that has the "shuffle list now" option