I had customized my Visual Effect settings in
Control Panel > Performance Information and Tools > Adjust Visual Effects
I discovered that after enabling all settings, Aero Peek worked. After toggling them all off and enabling them one by one, I discovered that only three are required for Aero Peek to work:
- Animate controls and elements inside windows
- Enable desktop composition
- Use visual styles on windows and buttons.
The one that I had turned off that was preventing it from working originally was the first one -- Animate controls and elements inside windows -- which was a little surprising. Also interesting was that "Enable transparent glass" does not
have to be enabled.