If your digging around Windows Live Messenger "Wave 4" bits, looking for a way to "turn off permanently enabled SmartScreen-based link scanner," Rafael shares a trick that involves a flag that disables/enables the Aero window border — just navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Live\Messenger and create the DWORD value AeroWindowFrameEnabled with its data set to 0 or 1.
For those on 64-bit platforms, don't forget you need to tack on Wow6432Node after the Software\ node, or you'll be fishing around in 64-bit waters. (Windows Live Messenger is a 32-bit process.). Given how poorly this works (e.g. can't move the window, no title bar), I'm guessing it's unfinished or on its way out," revealed.