I get it whenever Liam wants to do something with hardware.
Today was his second "from the ground up" computer build. He's been stockpiling parts for close to a year, saving up his allowance, Christmas money, etc. and buying stuff from the list he had made. Cooler Masters case, Asus motherboard, an AMD CPU (I think it's six-core), 8Gb of Crucial RAM, A high-end Radeon video card, etc.
So anyway, we got it together, went to start it up ... nothing. A little research later, we figured out that my guess about where the power switch cable plugged in on a motherboard with pins that didn't match what the diagram seemed to indicate was wrong. Fixed.
So then the main cooling fans come on at powerup, but the CPU doesn't seem to be getting power. Another 20 minutes of tracing cables and looking up instructions ...
Voila, it asks for an OS to be installed or to be pointed to a different boot device. So now that I know he didn't waste all that money on hardware that was either defective out of the box or incorrectly assembled (with my assistance and probably due to my oversights), I can finally sit down and have a heart attack.
All that work, and he's going to ruin it later tonight by installing Windows 7, the little shit.