if u have lots of chat windows open in xp so that a single button ohn your taskbar gives a 'stack' of windows when u click on it....and someone chats, ur msn button will flash.

 

if u click on the button while it's flashed 'on' (lasts half a second) 1 chat will be a different colour..if u click on the button when it's not flashed 'on', the stack will be the same colour, so u can't see who's just said something..

 

tis a useful feature on XP.