And the fan? Within 30 seconds, it spun down. Then stopped completely. Dead silent. It only came back on when the CPU actually heated up—exactly as it should have from day one.
Then, deep in a 2012 VAIO support thread (archived, in Italian), I found a real clue: "SNY5001 is the Sony Firmware Extension Parser. Without it, Windows can't talk to the EC (Embedded Controller) for fan curves and battery health." acpi\sny5001 driver
"ACPI? That's power management stuff. SNY? That's Sony. 5001? No idea," I thought. And the fan
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. Dead silent
I searched online and found nothing but old forum threads. One said, "It's a dummy device, ignore it." Another said, "Your laptop will explode if you don't fix it." Very helpful.
Right-click → Update driver → "Windows couldn't find drivers." Standard.