Check your screens have the same settings

This is something that some may know already, but others may find useful.
We have a fairly typical setup, with a laptop computer running Presenter and the data projector as the extended screen. Both are set to High Definition - 1920 * 1080.
We noticed a problem when displaying PowerPoint files. It only showed up if we were using PowerPoint to display them. The display on the projector was offset in the vertical direction, leaving a black band at the bottom and cutting off the top of the slide. If I displayed them through Presenter, they displayed perfectly. I could not reproduce this error on my home PC, which also has dual screens, with both set to 1920 * 1080.
We eventually tracked down the problem; the laptop display had a scaling setting of 125%, (some of the operators did not have the best eye sight!) while the projector had a scaling factor of 100%Switching the laptop back to 100% has cured this and we are now able to display PowerPoint files using either Presenter or PowerPoint equally well.
The lesson from this is to check that all your screen settings are identical, not just the resolution.