But, if you put something that'd melt under the extreme heat inside the CPU fan blades to stop them. The CPU would then smoke and melt, and the heat would cause what you stopped the fan blades with to melt, restarting the fan, but the CPU wouldn't work.
he he he!!!!!!!!!!!!!! I say, unplug all of the fans!!!!!!!!!!
and then plug them back in after the comp is dead, then the IT guy won't know it was you. That would be the best way, because pulling crap off of the board the IT guys might see...or ya, magnets...or water!
Could it be that your bosses son is a gamer, and reading this,And then on Monday all the pc's are all broke,When Daddy gets home he will sit at the dinner table telling the story to his son,And his son happens to be learning about Pc's on Computer forums.
This actually sounds like a lot of fun. THere are tons of ways to "break" a computer without making it too obvious. The best way is by shorting it out. Create a short by sticking a paper clip on the motherboard somewhere and power on or just drop a small screw in there and power it on. I've actually done that before. Ouch. Pull out some pins somewhere, capacitor, resistor, etc. Spray some water in there too. That will do it.