While taking IT classes at night, I was employed at a non-IT job. As a result, the owner of the company sometimes asked me to fix technology that was causing problems at the office.
One day I was asked to take a look at the owner's computer. It had been working fine the day before but would not turn on anymore.
I began by pressing the power button. As soon as I pushed it, I noticed the cooling fan in the back started to turn but then stopped right away. I had completed my first computer hardware class the semester before and could hear the instructor's words: "If the computer is not getting through the POST, it means bad power." My brain immediately concluded that bad power meant a loose wire or a bad power supply.
I didn't have a power supply tester, so I figured the best way to check for a bad connection was to unplug all the electrical connections off the motherboard and plug them back in. I took a picture of the "guts" of the computer to make sure I could put it back together again, then got started.
This computer was an older, custom-built gaming machine that the owner's son had given him and the owner had repurposed to use at his business. Midway through the task, I realized the wires I was pulling out were not the standard ones I saw in the computer lab -- it was custom wiring.
Horrified, I attempted to put the wires back but could not remember where they all went. I consulted the picture on my smartphone, but it didn't show the details I needed. After a few hours of frustrating work, I went to the owner and told him what I had done. He was gracious about it, but ended up calling a professional computer tech to fix both the original problem and the mess I had made. I felt sick as I watched the tech arrive and take the machine away.
The next day the tech dropped off the computer. I happened to be the one around to take the computer from him and inquired about the wiring. He told me it had been quite a job to repair it -- he had to pull the tech specs on the motherboard to get everything back together. After he left, I hooked the computer back up. It was the least I could do after making a royal mess.