Click through/behind Winamp

[Stupifier]

I remember a while back...like in WA3 days....I was able to hold a key and all clicks would pass directly through winamp to the window behind it. This was useful when Winamp is "Always on Top" and Trasparent. This way, I was able to click on stuff behind my Transparent Winamp windows without having to minimize winamp to reach the object. Does anyone remember how to do this or if this is still possible?