How to solve a problem
I used to get calls from my mother whose laptop settings, icon placement, and email account and so on had randomly changed since she used it last. I'd painstakingly help her through it over the phone, and sometimes I'd have to go to sort it out in person - an entire afternoon's worth. Though spending a bit of time with her is always worth it, this would invariably happen when I had no spare time at all.
Then I realised it was always be after my brother-in-law, also a techie, had visited. He'd piss about with the machine to suit himself or kids, and leave it in that state without telling anyone. Then I'd have to fix it. All so he didn't have to bring his own laptop.
I sorted it out by putting a password on it and refusing to tell him what it was.