On my first pc build I had to drove 2 hours back to the parts supply shop because after all was assembled the PC doesn't turn at all.
Just standing on the door the seller looks to me and ask: "did you read the first paragraph on the first page of the main board manual, the one on extremely gigantic font?"
The main board had a Jumper which is set on pins 1-2 to shipping and 2-3 for working, if you don't change the jumper, the board will not start at all!!! and really was a warning of half page, as my granma used to say: "si todo lo demás falla, lea el PUTO manual" (if everything else fails, RTFM!)
Never has been so ashamed on my life.
The only redeem was a client some time later; she call me a Tuesday afternoon asking:
"Hey, how many will cost replace the coaster of the PC, I know I will have to pay it and the warranty will no cover it because I put a big glass of juice on it, please give me a good price to replace it".
I get socked and completely confused, my mind start to spin "coaster?" when I reacted try to ask her which coaster (on the more polity manner) and she told me the one on the PC, the one which she pressed a button and come from the PC tower with a hole for the glass.
I can't believe her: SHE WAS USING THE CD-ROM DRIVE TRAY AS A COASTER!!!
That same client calls me a Sunday night because: "She was finishing her graduation paper and after saving she stand up and go to kitchen for a coffee and when return, the PC was turn off and do not start again", she was crying because she had to deliver the paper next day 07:00
By then I was 15 year old, so my father had to drove me to her house two towns away at 23:00, we got on her house with a replacement PC on a backpack (we only had a motorcycle by then) and tools ready to put her Hard drive on the new PC.
When I go under the table to try to diagnose the problem, I did find what the power strip cable was around the chair leg and when she pull the chair back, disconnected the power strip from wall. I connected it back, routed the cable away of the furniture and test the PC started OK, open the document and all was working fine.
Obviously I did charge her lot of money for the visit.