Thanks GLH-the annoying little devil is no more!!
Unfortunately the trouble is now back. Tried ctrl alt del & ended the bt notifier then rebooted & rebooted again to clear it but it came back.Then I did "run" msconfig & unticked "bt notifier" that way.When I rebooted I had a message saying "yahoo messenger cant sign in" & a panel asking me to undo the change I had just made so I am back where I started with the MCCWSA window not responding/closing on shutdown/restart. Looks like BT have to sort this one out.