I've had to step through the process of pressing the power button to turn a screen on... for the IT manager of a huge client. (He described it as the "clock" button, because it had a circle with a line on it.)

My old flatmate told me of an irate customer who insisted that he didn't need to plug his modem in because it was an internal modem.

Last week I had to teach a telecom engineer how to ctrl+c/ctrl+v to copy and paste. Technical support is fun in ways that some people wouldnt understand.