I happened to be at home for the last tech support call my wife received. She said nothing, smiled, and handed me the phone. Which I promptly took over to my Linux Mint machine, and played along (the menu items are similar enough), strung the poor sod along for a good 15 minutes, until he gave up and told me to call Microsoft.
It was at that point that I, still playing the unfortunate computer user, asked him if I should tell them I was using Linux. His response had us giggling for another 15 minutes.
// since 1993