I used to play formula roulette every time I dragged the fill handle, hoping Excel wouldn't misinterpret my intentions. Was I supposed to lock the column, the row, or both? Then, the dollar signs ...

The Alt+Enter shortcut isn't limited to new formulas you write—you can go back and clean up any messy formulas at any time.

If Excel is not recognizing functions after reboot, change calculation settings, disable Show Formula, run Excel ...