Erase the past

When you're shuffling files around willy-nilly, you're bound to accidentally drop one in the wrong folderor almost more irritating, errantly make copies of a slew of files rather than simply dragging them to a new location. Arrrrrrrrgh.

 

 Picture 1: Keyboard showing CTRL button

Rather than trying to track that missing file down or manually delete the legion of copies, whip out the universal Get Out of Jail Free card that, somewhat surprisingly, also works within Windows proper:  
Ctrl + Z
The keyboard shortcut undoes your last action, restoring order when chaos suddenly appears.

(Ctrl + C and Ctrl + V for copying and pasting, respectively, also work properly within Windows.)