Story when I worked as a 1st line technician:

Customer: "Yes hello, I'm trying to install Windows as instructed, but the installer is not starting"

Me: "Ok, have you tried pressing [button] at the bootscreen?"

C: "Yes, over and over, still nothing happens"

This was actually one of my first calls, so my co-worker stepped in to help while I listened.

Co-worker: "okay, so when you rebooted the computer, press [button] and tell me what happens"

C: "....okay, I think it's starting"

Co-w: "Great! I'll just wait until it's running"

A minute goes by, installer seems to be running, but then we hear a loud BEEP. It's so loud another coworker hears it from his desk, through our headsets. A moment goes by, and it BEEPS again. Then the sound begins again, but doesn't stop. It's like an air horn at full blow. We ask the customer what he's doing, but he cannot hear us over the constant beep. We're brainstorming what it could be, when he finally says something:

"CAN.. LET.. OF.."

Co-w: "WHAT???"

"CAN I LET GO OF THE BUTTON??"

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I think we laughed the whole day