Winamp keeps opening new windows/instances
 

I am on a new Vista machine, but every time I click on an mp3 in say, Explorer, Winamp opens a new instance of the player and begins playing, even if Winamp is already playing a song. Click on another mp3 and now I have 3 songs playing at once. This never happened in XP, is there a fix for this?

forgot to say, of course the box for 'allow multiple instances' is unchecked.