2011 saw a bewildering turnover in players at the club and the new year looks likely to be no different as new boss Boothroyd looks to steer the Cobblers away from the foot of League Two.
Midfielder Harding joins on loan from Wycombe Wanderers on a deal until the end of the season.
"Ben is a very cultured central midfield player. He is a good size and has played in promotion winning sides before," said Boothroyd.
"He is a good professional, he has a good amount of experience and I want to bring in players who are capable of playing at a higher level to help get us out of the position we are in."
Striker Akwasi Asante joins Harding in being available for the Bank Holiday trip to face Shrewsbury. Check out the head-to-head record of the two sides by clicking below.