Touchscreen works in Metro but nowhere else.

Running Windows 8.1. When I'm in the Metro experience (the Start menu, the Settings screen, or even Internet Explorer, for example) the touch screen works perfectly. When I'm anywhere else -- on the desktop, running Excel, etc -- I can see the screen registering a touch (it "splashes" when I touch it) but no action happens. If I tap on an icon on the desktop I see the "splash" but the icon isn't selected. I can't drag a window, launch an app, or control a button on a dialog box. Happens even in Safe Mode.

Ideas?