Ashley Young’s 25th-minute free-kick got the rout started, before Roy Carroll’s clearance a minute later fell to John Carew, who doubled Villa’s advantage from 18 yards.
Petrov’s superb strike put Villa out of sight 10 minutes later. The Bulgarian controlled Carroll’s clearance before letting fly from fully 50-yards out which arrowed past the beleagured Derby stopper and into the net.
Gareth Barry grabbed the fourth, tapping home after Carroll parried Gabriel Agbonlahor’s effort before Agbonlahor himself added the fifth 14 minutes from time.
The mauling was completed in the 85th minute by substitute Marlon Harewood who rifled home, right-footed in front of a half-empty stadium.