I doubt that slogan is copyrighted. You should be able to use it. Regardless, there is little chance that Winamp's attorneys are going to come after you, unless you're explicitly using it in a derogatory manner. Otherwise pretty much all of modern sampled music wouldn't be possible
Interestingly, the slogan itself was inspired by a song:
http://forums.winamp.com/showthread.php?t=223075