If you're going to use that client instead of something like Trillian or Miranda - you might want to take a look at Messenger Plus! - it's pretty slick - adds some features & gets rid of that stupid banner ad too...and it's free.
http://www.msgpluslive.net/

>On my PC, when using Windows Live Messenger, I have no advertisement. However, on my laptop, I see it. Anyone would know what could be a factor on that?