Ok, so she wasn't a paying client, but I do basic tech support for my non-geeky mom.
She called me frantic the other day saying her computer had died. I mean she was full blown freaking out. I told her to calm down, I couldn't get over there that same day, but I could the next day.
So after work I picked up my son and we went to my mom's house to diagnose the problem. She told me that the monitor would come on just fine but that she wiggled the mouse and nothing happened. That got me thinking, I checked cables just in case, and then just hit the power button on her computer because I realized that the tower was off.
She saw the monitor come to life and thanked me, and I just laughed and told her to check the actual computer next time, someone had just left the monitor on, but the PC was off which was why she didn't see anything on the monitor. I still giggle about it and it happened almost a month ago.