Preston had the early chances with Callum Davidson firing a 30-yard shot off target and Danny Pugh hitting a dangerous free-kick which was headed narrowly wide of his own goal by Derby striker Steve Howard.
Preston captain Graham Alexander hit a shot off target from a Pugh corner.
Ex-Preston loan player David Jones hit an innocuous free-kick straight at Carlo Nash but he juggled with the ball and it led to Michael Johnson heading against the bar and Sean St. Ledger clearing before Jon Stead had a shot cleared.
Stead had another shot off target before Preston got their best chance of the first half.
Howard was booked for foul on Davidson and Derby's 18-year-old midfielder Giles Barnes had a 20-yard right-foot shot which went off target.
Davidson was booked for a foul on Stead and Howard headed over with Matt Hill also shooting off target.
Dean Leacock was booked for dissent after a foul on Ormerod with Ormerod also getting booked seconds later.
Derby were awarded a penalty just three minutes later when Liam Chilvers, who looked outside the penalty box, fouled Stead.
Howard hit a low right-foot penalty to Nash's left and he got a touch but the ball ended up in the back of the net.
Preston pulled a goal back with ten minutes left when Nugent latched on to Alexander's cross and scored from five yards but the late surge couldn't prevent Derby taking all three points.