...neighbours Rushden & Diamonds.
McDonald is a product of the Nene Park youth system, and former under-18s captain, who spent the end of last season on loan at Zamaretto League Premier Division side Banbury United.
McDonald is a Welsh under-17 international who started in their 2-2 draw against hosts Turkey in a UEFA Elite qualifying tournament in 2009. He then went on to play in their 3-0 victory against Romania in the same tournament.
He also joined the Welsh international pre-season tour to Denmark prior to the 2009/10 season, playing the whole of the game against Iceland.
McDonald's performances during the 2008/09 season won him the `Alan Thomas Most Improved Player of the Season` award at Diamonds.
During the 2009/10 season he went on loan to Wingate & Finchley and later Banbury, and after signing a professional contract in 2010 he went on to make his league debut for the Diamonds against Wrexham.
Last season began with an injury, meaning McDonald had spells on loan at AFC Sudbury and Banbury in order to regain his fitness.
Manager Graham Drury moved quickly to snap up McDonald and said: "Ainsley did well in his loan spell at Banbury last season but when he went back he became a bit disillusioned at Diamonds because of a lack of first-team opportunities. We're hoping we can come in and do well for himself and we can get a smile back on his face.
"He is another six foot-plus defender and can play on either foot so he's comfortable in either full-back position. He is strong in the tackle and quick and will be a good asset to the squad."