When I was in tech school, some guy from the nursing school (same building) came over and said their new software wouldn't work. The head of our department sent me over to take a look. It didn't take me very long to figure it out.
"Your new software won't run under DOS 3.3," I told him. "It needs DOS 5.0."
"Just make it work."
So I dutifully upgraded the operating system, started the software and played with it for a few minutes to showed him that it worked, and left.
About an hour later he stormed into our classroom ranting about how nothing else worked. I told my teacher what I'd done and we both (correctly, it turned out) surmised that the other software still only ran under the old DOS. This seemed strange to me, but eventually we figured out that it had something to do with the different command.coms.
"You told me to make it work," I said bluntly. "You didn't say anything about the other software you had on there."
He literally shouted his displeasure at me, and then yelled at my teacher "how are we supposed to fix this?" or something like that. He told the guy, "Upgrade your other software. I have a class to teach." And with that, he was dismissed. I never saw that guy again.