Goals from Jack Baker and substitute Kadeem Price gave Melton which could turn out to be one of the best results of the season come next April.
Co-managers Tom Manship and Jon Stevenson expected a tough test as they pursue five league wins in November to get them back into the promotion places.
Harrowby had thrashed promotion rivals Lutterworth a fortnight before and came to Melton with confidence.
The first half was a tight affair with both defences coming out on top.
Harrowby had the first real chance after just 10 minutes when Kelly turned the Town defence, but his ball across the six-yard box was missed by Harry Wakefield.
Melton then produced their first chance when Manship’s free-kick from the middle of the pitch found Reeve who teed up Hill, but he fired over the bar.
Both teams were finding it hard to break the other down and the only other really opportunity of note came 10 minutes before the break when a Harrowby corner was flicked on by Slater.
Peet punched the ball away, but Brooks returned the clearance back towards goal where Peet again cleared the danger.
The half-time team talk clearly changed the game for Melton as they came out with a new game plan which allowed Jordan Leaver to see much more of the ball.
His cross found Thorpe whose volley just shaved the crossbar, and six minutes into the half, Hill was played through and got clear of the defence.
Hill looked to be tripped as he shaped to shoot, but to the home supporters’ dismay, the referee deemed the challenge fair.
Harrowby almost broke the deadlock in the 58th minute when Wakefield got free of Melton’s back line and hit a low shot from the edge of the six-yard box which hit Peet’s outstretched feet.
The resulting corner found Briers whose header was inches over the bar.
But then a classy Melton move brought its reward after a quick break down the right.
Cobb’s low cross was picked up by Leaver who played a beautiful ball for Baker to slot a low shot under the oncoming Sam Andrew for 1-0.
Minutes later Peet’s goalkick found Leaver and his rasping shot beat Andrew but shaved the post.
Rigby caused problems down the left and from one of his crosses into the area, Reeve chested down and his half-volley was blocked on the line.
Manship took the resulting corner and Sam Wilson rose to plant a bullet header past Andrew to give the hosts some breathing space.
Sub Price could have made it three, but his half-volley was brilliantly saved by Andrew with six minutes remaining.
Melton face three games in the next two weeks which could provide a handy platform in Division One, starting at Rushden and Higham United on Wednesday evening (ko 7.45pm), which could take them within a point of top spot.
Then they visit fourth-placed Aylestone Park on Saturday and then welcome the current league leaders Anstey to Melton the following Saturday.
Town: Peet, Westwood (Cobb), Rigby, Manship, Punter, Wilson, Baker, Hill (Heath), Reeve, Leaver (Price), Thorpe.