How do I close required applications when doing upgrades?

Every other time I want to do a critical upgrade for my Mac Office 2011 (v14.2.1), an error message pops up:
These applications must be closed before the software can be installed… Close these applications and try again.

But actually I have not launched any of them.
Can anyone tell how to end them to finish the upgrades?

I always shut off the machine and restart it to do the installation of updates. Have you tried that?

The most effective method, I suppose, to end the processes it to click Applications > Utilities > Activity Monitor.

I agree that the fast and simple way to do this is to restart the desktop.