@MKop

Sometimes its not possible to keep a user 100% working and 100% happy when upgrading/updating software.
Then the communication skills of the IT department come looking around the corner.

As i see it there are 2 sollutions:

  1. Leave all computers turned on after office hours, then deploy at 21:00 or so.
    That way the computers can reboot what they want and no users are mad

  2. Communicate that the anti virus package is getting upgraded but that it needs a forced reboot of the system. This reboot is absolutely necessary to be able to keep protecting the users from virusses and other malicious software which could potentially destroy their documents.
    The AV software is hooked into the OS in such deep level that a reboot is just necessary, no questions asked.
    It takes tops 5 minutes to reboot right? Most people take longer to get a cup of coffee or go for a smoke.

You can possibly also deploy it during lunch time when everybody is in the cafetaria