A friend finished his high-level (banking) client meeting and the head honcho asked him for a little help with his PC. They went to his office.
"For the last few weeks I've had a mouse problem: I move the mouse left, the cursor moves right; I move it up, the cursor moves down.", he complained.
My friend was puzzled for 5 nanoseconds; then he turned the mouse round so that the lead was at the top..."