Shoutbox

That's because xfire injects itself into the game trough DirectX, msn doesn't use DirectX to draw it's windows. And a plugin or any other extension won't be abled to change this.

The most that could be created was a new window created in DirectX by a plugin that will relay the messages of MSN to this window.

However it's not easy to inject a new window like this into a game with DirectX.