I Deleted Something On Accident Instead of Uninstalling It?

I recently bought a new laptop that came equiped with Windows Live Messenger 2011, I rather dislike this update and opt to go with 2009 instead, but accidently deleted the file instead of uninstalling it. When I restart my computer and turn it back on the MSN pops up asking me to log in, but I can't find the file in my folders anywhere so how do I uninstall it if I already deleted it? It wont let me install the 2009 version because I didn't uninstall this one technically.