Acpi\sny5001 Driver: ((exclusive))

"ACPI? That's power management stuff. SNY? That's Sony. 5001? No idea," I thought.

I went back to Device Manager. The yellow triangle was gone. had moved to "System devices" and was now named Sony Firmware Extension Parser . acpi\sny5001 driver

I installed it. It took 10 seconds. No reboot needed. acpi\sny5001 driver

That's when it clicked. The fan wasn't broken. Windows simply didn't know how to control it because the driver was missing. The laptop was running a "safe mode" fan profile: ON all the time. acpi\sny5001 driver