It is always a good idea to power on any PC/laptop/desktop at LEAST once a month so that whatever updates/patches/fixes are out there can be downloaded. I don't know how long updates sit waiting to be downloaded (probably not years) and at times Microsoft has announced that certain operating systems will no longer be updated. Computers have a way to adjust the audio so you can mute sounds. Computers don't typically make loud/unusual sounds when booting up. Not clear if the Op was referring to some sort of audio issue or if there is a mechanical problem causing something like the fan to be rubbing against the housing. Any sort of strange mechanical noise probably requires a repair technician to see what is wrong and how to best fix it.
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