Shoutbox

I noticed that when my friend talks to me on Windows Live Messenger he is busy, but when he starts typing it changes to Available then when he is done he goes instantly back to busy.
I want to know how he can do that?

He probably has the "Show me as busy and block my alerts when I'm running a full-screen program or presentation settings are turned on" option turned on.

You can find it under Tools -> Options -> Personal -> Status in Messenger.

Is there any other way of doing that without having a full-screen program?

You could, I believe, with a Plus! Script detect whether a chat window is in focus and handle the status change on that basis.

Or if you wish to base it on typing, you could use the EditText property of ChatWnd object provided by the Plus! Scripting Interface to check whether the typing area has any text or not and change the status.