I have frequently returned to my locked, idle Surface Book after being away for an hour or more to find it is running its fans at full speed. The screen is off and it should be doing nothing. When in this state, it is slow to respond to any form of wake-up signal. Ultimately, once unlocked, the fans will turn off, suggesting the process that had been using the CPU has ended. I've not yet been mindful enough to have Process Explorer tracking what's going on, but I'm curious if others have seen this behavior and already have some troubleshooting to share. Thanks!