After some consideration, I think you might be right! Good forensic work, there! The giveaways I should have spotted are:

• A taskbar appears below the Paint window, but not below the IE window. This suggests that the IE window was not maximised.
• The icon in the IE “maximise” button also suggests this.
• In the taskbar below the Paint window, the Internet Explorer window is focused.

So it’s still a little strange, but nowhere near as strange behaviour as I’d originally thought. And I’m still not sure about the TIFF file format (why, user, WHY?).

Thanks for your thoughts, Spencer.