Current and former members of the University of Rhode Island’s Greek system have donated nearly $107,000 to the South County Habitat for Humanity. The university said Tuesday that more than 500 students from all 24 of the university’s fraternities and sororities participated in the annual ‘‘Pound the Pavement, Pound a Nail’’ walkathon. The event raised more than $53,000. Two anonymous URI alumni who were part of the Greek system on campus matched the funds. The money was given to the organization over the weekend at a house dedication at Old North Village on the edge of campus. It will help build two more homes.