It's bugged me for a while I think I should report this.
I'm not good at explaning so I'll just quote, what is Aero Snap:
"To make it work, just click the title bar of a window and drag the window a-a-all the way to the left side of the screen. Windows 7 docks the window to the left side of the screen and shrinks it to half size. "
I know this feature works in ALL windows except Mp3tag.
In mp3tag, Aero Snap only works when I use the keyboard shortcuts.