The visitors took the lead three minutes before the interval when Gary Phillips parried a Lee Williams shot and Joseph Odegbami was on hand to slot in the loose ball.
United improved in the second half and Matt Hayward and Stacy Joseph forced a couple of good saves out of Desborough, but twelve minutes from time Paul Cobb raced through to score his 27th goal of the season to put the result beyond doubt.
Aylesbury United
Purfleet
Boreham Wood
Enfield
Bromley
Heybridge Swifts
Carshalton Athletic
Hendon
Grays Athletic
Dulwich Hamlet
Harrow Borough
St. Albans City
Hitchin Town
Yeading
Kingstonian
Oxford City
Staines Town
Sutton United
Yeovil Town
Bishop's Stortford