Thanks for replies.
Allan - FileHippo lists the program as: Windows Live Messenger 2009 (14.0.8089). As mentioned, I've never used it (my version is 4.7, so must be pretty old and been dormant). I followed instructions given in your link to pchell, as far as I was able, but that seems only to have removed it from the startup program. The icon that has been appearing in the Task Bar ("You are not signed in") has gone.
Computer_Commando - I've looked again and there is definitely nothing listed in Add/Remove Programs under Windows Messenger.
Just seen latest post - BC_Programmer - it is in Components (I didn't look there). I have cleared the ticked box and I think that has done the trick.
It's not really that important, but it is irritating that I cant figure out how to do it.
Allan - One other point - why do not use update managers?