A bit of a hidden feature in Windows 8: you can actually "quit" Windows Explorer.

Right-click the (empty) taskbar while holding down Ctrl+Shift to reveal Exit Explorer as an additional menu item. Clicking it will then end Windows Explorer, leaving you with a blank screen, same as ending explorer.exe from the task manager.

You can then call up task manager (Ctrl+Shift+Esc), and start Windows Explorer again (File > Run > explorer.exe).