Dude same here. I usually say stuff along the lines of 'yea it took me forever the first time to figure it out' or 'it's a common issue that a lot of people have, I'll get it sorted in a sec for you no problem'. Make it seem like they're not stupid, regardless of the truth and then fix it, keeps em happy and more willing to cooperate with you as well.

I also talk through what I'm doing and if they show interest I'll teach them so they can fix it in the future, 'ah I've seen this before, took me like a hour to figure it out on my computer, for me it was a chrome update that broke how downloaded files open. Here let me right click the file, and go to open with, we hit Adobe pdf and check the always open with this program button, that should do it let's test it out. OK seems like its good to go. Let me know if you have any more issues'. If they don't show interest then it's no problem.