If you are powering off a very old system that spends most of its life powered on, don't let the hard drives or power supply cool down. Do your best to keep you

If you are powering off a very old system that spends most of its life powered on, don't let the hard drives or power supply cool down. Do your best to keep your work as brief as possible and get the thing turned back on before it assumes room temperature. These components tend to run the hottest, you can have cold solder joints contract and stop making contact when they cool down. Also check any socketed chips and make sure they are fully seated. Chip creep happens when frequently thermal-cycled boards cause the IC's to slowly lift themselves out of their own sockets.