Shoutbox

Surely using the 'Favourite's Bar' in the web browser is a much better way of accomplishing this, by just adding it as a favourite?

Or if they want it to be done exclusively in Messenger (which is a bit backwards, but still...) perhaps using Messenger Plus! Live's QuickText feature, creating a short string such as "(link)" which will automatically paste the text of the [I'm guessing] long link into the conversation window from where it can be clicked on?

There are FAR better ways to open a link than modifying Windows Live Messenger to add an extra button for it