Everyone knows OS and software, browsers, etc all use way more RAM than they used to, and arguably more than they rightfully should. Bloatware, etc.
I saw something recently that alleged MS puts a lot of shit into PCs that say they are doing one thing but are really doing another.
It would be wild if they are basically using the PCs of the world to do something like crunch numbers, mine bitcoin, etc. Oh, hey, this guy has 12 gigs of ram and is only "using" 4, that's 8 for us to sap.
RAM usage isn't (generally) anything to worry about. 100% CPU on the other hand is a problem.
It's difficult to really go into all of the surgery that you'd need to track down what malware or misbehaving program/driver might be causing it, so my suggestion would be to reinstall Windows. If you're getting 100% CPU usage when doing nothing, you've got a problem.
Okay cool. Thanks for the info man. I think I'll be dusting it off this weekend, and give a reinstall a shot.