Jake Bettles gave Ar Tarn an early lead, only for Jack Wisniewski to bring the Doughboys level.
But Desborough took control before the break with Jason Turner restoring their lead and then John Dean struck to make it 3-1 at half-time.
Dan Bendon reduced the arrears early in the second half but a Turner penalty made it 4-2 before Dan Grainger’s fine strike sealed the points, although Deven Ellwood pulled another back for the Doughboys, who were beaten for only the second time this season.
It was a day to forget for Rothwell Corinthians, however, as they slipped to a third defeat in a row when they went down 4-0 at Wisbech Town.
It was a fine day for Raunds Town in Division One as they moved into fourth place with an excellent 2-0 victory at fellow early high-fliers Long Buckby.
Another team right up there are Thrapston Town after they edged out local rivals Rushden & Higham United 2-1 at Chancery Lane on Friday night.
Jedd Whiteman and Cory James were on target for the hosts with Ryan Kalla pulling one back for the Lankies.
Whitworth capped a fine week, which saw them beat Peterborough Sports in the Knockout Cup, by claiming their fourth win of the league season as they beat Bourne Town 3-1 at London Road.
Elsewhere, there was disappointment for the local clubs.
Irchester United went down 3-1 at leaders Oakham United and both Burton Park Wanderers and Stewarts & Lloyds were hammered 6-0 at home by Olney Town and Buckingham Town respectively.