This reminds me of a time in my early days tinkering with electronics and pcs, i was literally a little more than a toddler, and my dad had a small pc selling and repairing business.
One customer brought his pc in for support, because it was "randomly freezing and had to be powered off". It was a big full tower with 5 5inch bays and 2 or 3 floppy bays in the front. My dad was trying to investigate a software issue, after all these were the days of the freshly shipped Windows 95, but it seemed nothing was out of place, all the drivers were looking fine and a fresh re-install of windows didn't solve the issue.
Meanwhile, being a curious creature, i crawled under the desk to look inside that chungus while the case was open (no shiny glass side panels in those, the two sides and the top came out as one piece)..... and EUREKA, the little cpu fan (think Pentium I 133MHz) was not spinning.
A quick replacement, et voilà, the machine got back to full performance.
I even had to make the call to the customer telling what had been wrong with his pc.
I miss those days, now i'm a sysadmin in a medium-to-large company and i have responsibilities... oh well, TGIF, cheers!