Arthur had a short spell with the Cobblers under Gary Johnson but was allowed to leave Sixfields after Aidy Boothroyd's arrival.
“I feel I have something to prove," he said, quoted on the Get West London website.
"He let me go for a reason and it’s up to me to show what I can do."
After playing for Havant & Waterlooville, Arthur joined AFC Wimbledon in the summer and has been used mainly as a substitute by manager Neal Ardley so far this season.
Boothroyd, meanwhile, is hoping that the stable base provided by Mathias Doumbe and Paul Reid in the heart of defence against Morecambe last week will be the springboard for Town to start scoring goals at the other end of the park.
Previewing Saturday's game he told BBC Radio Northampton: "We need our forwards, whoever comes in - if we do get someone in - or whoever gets picked, to start scoring goals."