Garages, they have a lot to answer for.
I maintained a local M.O.T. garages computers for a couple of years, but generally only had to deal with the office equipment which was what I would call run-of-the-mill support. Though one day the manager asked me to look at the box installed in the garage, you know, the one that held all the M.O.T. data etc. It was overheating and to cut a long story short it mirrors the main story above. Opened up the box, couldn't even see the motherboard/CPU block or PSU through the compounded brake dusr and gunge. BUT I got it working after a good steam cleam (joking).