You may be correct sleep mode might not work to stop the bootup message, but it's easy to try. Just put your computer to sleep and then wake it up to see if you get the message.

As for the message reappearing several times during the day, I don't have any real suggestion.

If you have someone who is really obsessive/compulsive, assign them the task of figuring it out. :7

When I run into something like this on my computer, until I am able to figure out the solution, I have a "button pushing" program that dispatches most popups, and a whole lot more, in a fraction of a second. But if you've never found a need for an automated button pusher, then this is probably not an option for you.

Jim.