uninstall
I should have said how to uninstall Messenger, shouldn't I?
Go to Drive root/Windows/INF and locate the file SYSOC.INF. Double click the file to open it in Notepad. In the "Components" section, you will see:
msmsgs=msgrocm.dll,OcEntry,msmsgs.inf,hide,7
Remove the "hide" part so that it looks like:
msmsgs=msgrocm.dll,OcEntry,msmsgs.inf,,7
Save the changes and exit. Take a backup of the original SYSOC.INF, just in case.
Now go to Add/Remove Programs in the Control Panel, click, Add/Remove Windows Components, when the list is populated, scroll down and untick "Windows Messenger".