Messenger Live, Vista Ultimate and usnjsvc error

I have a computer loaded with Vista Ultimate. I use MSN Messenger Live daily.
For the last few weeks, when I start Messenger, I was greeted with a message
that an upgrade was available. I continued working in Messenger and told the
app to go ahead with the upgrade process. After a few minutes, I would get a
message pop up stating the upgrade failed, do I want to close the app. I
always said no and the message went away and Messenger would restore to the
screen from the taskbar. Everything worked so I just minimized and pressed on.
Starting a few days ago, when I attempt to open Messenger, I'm greeted with
a message that Messenger can not continue until the upgrade is completed. I
instruct the machine to continue with the upgrade. I have to close Messenger,
Outlook and anything I'm working on before it will continue. After watching
it download and start the upgrade, I'm greeted with the message Service
'Messenger Sharing Folders USN Journal Reader services' (usnjsvc) can not be
stopped. Verify that you have sufficient privileges to stop system services.
In checking the C drive, I have full ownership and security privledges of
the entire hard drive and subsiquent folders. There is only one account on
this computer and mine is an admin account. Looking in the services folder, I
see nothing pertaining to Messenger Journal Reader services or usnjsvc or any
other related service to actually stop. In opening a cmd window I have typed
in sc stop unsjsvc and get the reply that access is denied.
HOW do I get this service to stop so I can complete the uninstall of the old
version of Messenger and get the new version loaded?
Thanks.