Isopropyl alcohol and a toothbrush. Turn off power to the PC. Hold power button for a minute. Unplug and disassemble. Get one of those chemistry squirt bottles (google lab wash bottle) to put the alcohol in, squirt it on the place to clean, brush with the toothbrush. Repeat until at desired cleanliness. Then take canned air and spray out under all the parts. Allow to dry. It’s dry when you can spray under the big components and not get any alcohol out.

I used to assemble, test, repair, and clean PCBs of all shapes and sizes. That’s what we did when we had to spot clean a board after a repair.

The jankiest way I’ve cleaned a PCB was to run it through the dishwasher without detergent, then wash it down with RODI water to demineralize, then alcohol to displace the water. It works, but you gotta be damn sure that you’ve washed away any mineral deposits and given it plenty of time to dry.

I ran the back of the napkin math on this for my org (US local government). Not really possible unless you’re just doing office work. Microsoft is so deeply ingrained in govtech that you can’t even shrink your footprint. That’s not even counting the political and cultural buy-in before you start the lift.