Oh... wait... the PC has been sitting idle (on but not in use). After quite awhile, I got this banner across my screen indicating that the computer would have to possibly reboot several times and offering to start. We're off! Rebooted. Now "Setting Up".
What's interesting about this is that there was no clear indication that something was indeed continuing in the background (some sort of preparation leading up to the aforementioned banner). As well, the hard drive wasn't particularly active. I did notice an unusually "excited" WiFi adapter, its LED flashing away... but that happens frequently enough without apparent reason.