Derby thrashed a lacklustre Watford to secure their first home win in more than five months.
Centre-back Richard Keogh glanced in a header and Jeff Hendrick also nodded home to give the Rams the upper hand.
Conor Sammon chipped a delightful shot over keeper Manuel Almunia to extend Derby's lead.
Will Hughes and Jamie Ward both tapped in to put the game beyond doubt before Matej Vydra drove in a late consolation goal for Watford.
Derby's last win at Pride Park had come when they beat Crystal Palace on 24 March but they ended their wait for another in emphatic style.
Keogh converted from Ward's cross to set manager Nigel Clough's side on their way before Hendrick's far-post header back across goal beat Almunia.
Sammon's stylish finish after a surge towards goal gave him a goal on his home debut and left the visitors shaking their heads.
Watford's predicament only got worse when a Ward effort was tipped on to the post by Almunia to leave highly-rated prospect Hughes a simple finish for his first goal for Derby.
Ward was rewarded for his performance with a goal before Watford denied Derby a clean sheet through Vydra's shot.