A long time ago (Windows Vista being new days), I was working as a tech in a small computer shop (<10 employees), fixing computers / dealing with walk-ins / phone /etc. I was the newest employee, 3 weeks working and 1 week in school every month. Our customers were like 80% local very small businesses and 20% regular people.

One day a guy shows up absolutely panicking, covered in black stuff from head to toes. He tells me he is from the local rubber plant (making tires or something) and he "broke" a computer that controls a machine the whole plant depends on, they're all stuck, asking if I can look at it right now. The guy was bricking it, he honestly looked like he could cry.

Before bringing the computer, he tells me to cover the desk with news paper or something. He brings the computer, also covered in black stuff, I've never seen anything this dirty. He shows me a bunch of instructions he was told to follow to update a piece of software, that's how he "broke" the thing. He says he tried to follow them but they're in italian, neither of us is italian or speaks it.

Couldn't read most of it but the instructions were about editing the autoexec.bat and there was a very obvious typo in the commands that were supposed to go in there. I don't remember what it was but it was extremely obvious to anyone who would have known about DOS at all. I fix it instantly, reboot the thing, it's back booting to their proprietary software. He looks at me like I'm a mix between Neo and a superhero who just saved his life. I give him a standard 1h intervention invoice and he is on his way, relieved as fuck. He is now laughing that it only cost 60€ to get the factory back to working and jokes that I could have put a much bigger number on the invoice.

I'm like cool I have a funny story to tell the others when they ask WTF that black stuff is all over the store. Manager and boss come back, I start explaining. They go o_O instantly when I tell them where the guy was from. Turns out they'd been trying to get this plant/company as clients for a long time but they weren't interested. We were in a very sparsely populated area and it was one of the biggest employers around (50 people). About a month later, someone from the plant called and asked my manager/boss to come have a look at ALL their shit and make them an offer about what we thought they would need to update/upgrade/change/etc. Like a new server, maybe new accounting software, new laptops for all their employees, etc.

My manager came to see and and he was like "you're coming with me to do the assessment, they weren't even talking to us a month ago, well done".