Ben Williams gave Harborough the lead at Bowdens Park but Justin Dowling headed home a free-kick just four minutes later to level things up before the break for the Doughboys.
And Dowling was the hero as his goal five minutes from full-time wrapped up three precious points for Jon Mitchell’s team.
Rothwell Corinthians also tasted victory on the road as they claimed an impressive 1-0 win at Boston Town.
Rob Foster grabbed the only goal of the game on 25 minutes while Boston had Lori Borbely sent off during the second half.
Stewarts & Lloyds played their first home game for two-and-half months and maintained their push for promotion in Division One with a 1-0 victory over Whitworth at Occupation Road.
The Flourmen’s resistance was finally ended in the 75th minute when Lee Garvie grabbed the only goal of the game.
S&L remain nine points behind second-placed ON Chenecks after they claimed a 2-1 success over Irchester United.
The hosts took the lead through Tom Caton but Nathan Heycock levelled for the Romans on the hour.
However, Chenecks found a winner with 13 minutes to go through Ben Lewington.
Rushden & Higham United maintained their top-five position with a dramatic late win at Bugbrooke.
There seemed to be few problems for the Lankies after they took a 2-0 lead into half-time thanks to goals from Jack Dyson and Jory Mann.
But Bugbrooke staged a second-half fightback and made it 2-2 when Jamie Hall struck twice in the space of eight minutes.
However, the visitors snatched the points thanks to Lewis O’Dell’s goal on 85 minutes.
The local derby at Chancery Lane ended goalless as bottom side Burton Park Wanderers held hosts Thrapston Town to a 0-0 draw.
Raunds Town missed out on a place in the NFA Junior Cup final after they suffered a 1-0 defeat at Netherton United.
Ben Panting scored the only goal of the game just before half-time to ensure the Peterborough side advanced to the final.
And it will be an all-Peterborough affair after UCL Division One leaders Peterborough Sports won the other semi-final, but not before they had been given a thorough examination by Teamwork Sports & Trophies Northants Combination Premier Division side Weldon United.
Weldon held a Sports side who have won all 21 of their league games this season to a 0-0 draw at Rockingham Triangle.
But Sports held their nerve from the penalty spot as they triumphed 7-6 in the resulting shoot-out.