wireless switch on laptops
Amazing how many times the little switch found on laptops to turn WiFi off is responsible for hours and hours of troubleshooting to figure out why a computer can't connect to the Internet anymore. I have seen it happen so many times. It's simplest thing, but always the last one you think of looking at. Manufacturers should come with a better way to do this, either hide the switch away so it's not so easy to flip it accidentally, or tuck in somewhere else, or do it via a BIOS setting, or make it a BIOS boot option.

