Good Day, 

We have Macrium Reflect installed on a general purpose computer that is used for Powerpoint presentations in the Boardroom. Every hour, or so a pop-up window keeps appearing on the lower right of the screen with "Macrium Reflect version 7.xxx is available for download" or something close to that.

Great advertising, until it interrupts the CEO's presentation several times during a Board of Directors meeting and several VP's yell at me as a result. As Reflect checks for new versions when I boot it up, I don't need to see this. I was told in no uncertain terms to either suppress the pop-up or remove the software. 

How do I stop it from popping up?

That was introduced for 7.2 and fyi you posted this in the V6 forums, but you just go to Edit Defaults > Update and uncheck the option for hourly checks.  Be aware though that if you disable that, Reflect will only check for updates when you launch it interactively.  It will NOT check for updates when scheduled backups run in the background.