Northampton claimed the last remaining League Two play-off spot with three second-half goals versus Kidderminster.
Town piled forward from the off but could not find the crucial goal.
Striker Andy Kirk went close on three occasions before he broke the deadlock when lashing home a shot after Fred Murray's initial header was saved.
John McGrath's dismissal for a reckless challenge on Charley Hearn changed the game and Town took advantage, Josh Low heading home two Eric Sabin crosses.
Northampton: Harper, Togwell, Willmott, Chambers, Murray, Low, Rowson, Williamson, Hearn (Sabin 77), Kirk (Hunt 88), McGleish (Richards 88).
Subs Not Used: Bunn, Galbraith.
Booked: Hearn, McGleish.
Goals: Kirk 68, Low 85, 87.
Kidderminster: Lewis, Weaver, Sall, Hatswell, Burton, Chambers, Keates, McGrath, Sturrock (Hollis 86), Christie (Foster 66), Rawle.
Subs Not Used: Jones, Danby, McHale.
Sent Off: McGrath (74).
Ref: T Parkes (W Midlands).