Damien McCrory played in a cross from the left and Reed just had to tap it in from six yards out for a late, late winner.
So long was added on at the end of the match due to a head injury to Burton substitute Jimmy Phillips. The midfielder was involved in a clash of heads in the second half, received treatment but then had to come off with five minutes remaining and was taken straight to hospital.
It was a game of few chances until a lively ending. Accrington's Marcus Bettinelli, on loan from Fulham, was the busier goalkeeper.
The first chance fell to former Stanley striker Michael Symes but his 25-yard strike by was pushed out by Bettinelli who was quickly in action again diving superbly to keep out a Rene Howe volley.
Stanley striker Kal Naismith tried his luck with a shot which was not too far off target while the last chance of the first half was an Adam McGurk free-kick from 25 yards out which Bettinelli grasped at the second attempt.
Reed thought he had broke the deadlock after 52 minutes when he got his knee to Symes' goal-bound header but he was ruled offside - to much frustration on the Burton bench.
Both teams looked for the winner with James Gray hitting the woodwork for Stanley six minutes from the end and Bettinelli tipped over Howe's effort before Reed struck.