A jump in Microsoft helped lift the Dow Friday. Microsoft had its biggest gain in four years after longtime CEO Steve Ballmer said he will retire. Ballmer took the helm of the software giant from founder Bill Gates in 2000. The market surge came at a good time, as stocks have sagged in August on concerns the Fed will start to pull back its stimulus. But minutes from the central bank’s July meeting gave no clues on when. Earlier in Friday’s session, indexes stumbled after the government reported a plunge in new home sales. And major builders fell after Commerce said Americans cut back on buying homes last month as mortgage rates rose.