I've been getting annoyed with my Windows 10 SP3 running hot due to high CPU usage so today started to delve into it. This doesn't happen all the time, something triggers it and it stays high and hot until I reboot. I decided to stop numerous services one by one using the Services app, selecting non-essential looking services (no science here - just guesswork), and stopping them while also running Resource Monitor to see what, if any, difference it would make to the CPU use. System Interrupts was shown in Resource monitor constantly using 18-23% CPU for the previous hour. I had closed all running programs (Outlook, Chrome etc etc) and left everything to sit for an hour to stabilise before I started stopping services. After stopping a bunch of services with no effect at all, I stopped Windows Audio. CPU use immediately dropped to 2%, but then rose back up again to 20% after a few seconds. Strange. I then stopped Windows Audio Endpoint Builder and the same thing happened - CPU dropped to 2% again. Interesting. Going into Device Manager > Sound, video and game controllers > Realtek High Definition Audio, I disabled the driver. CPU (specifically System Interrupts) immediately dropped to 2% then back up to 20% after 2 secs. I then enabled the driver again, and CPU immediately dropped back to 2%, and then up to 20% after 30 secs or so. So it looks like there's something very screwy going on with the audio driver. The driver version I have is 30/6/2015 126.96.36.19943. It's odd that disabling then enabling the driver causes the CPU to drop to "normal" levels, but then it shoots back up again after a little while. I'd have thought disabling it would cause it to stay permanently at low levels. I suspect that there's something which is accessing the audio driver which is causing the problem, rather than the driver itself as I can't see how it could use CPU if it was disabled (though I'm happy to be enlightened on this). However, fiddling with the driver definitely has a dramatic, though temporary, effect on CPU use. A reboot of the machine puts everything back to normal. I've yet to figure out what the trigger for the high CPU usage is. I didn't have this issue prior to Win10.