1. You Break it You Bought it
When you sit down to fix a problem that presented as a simple one you are creating a contract. Not a legal contract, but a social one. The computer owner is trusting their computer with you. It's their baby, and you're the doctor. So you sit down, and begin to fix a problem.
In the process, something else breaks. You fixed one thing, but something else goes awry. What's the best part? Neither you nor the user notice it is broken until a day later when they call you to blame you for breaking something else.
"I thought you were going to fix it." They complain.
