Preferably for free? Can this be done? I've heard TeamViewer is the easiest way to do it, but that it isn't secure. Also, if another user is logged onto the machine, it's a no-go. Is that how it is ...

With Find My Device, one can locate their stolen device if they have connected their Microsoft account to that device and have enabled Find My Device. If you want to remotely Lock or Unlock a Windows ...