WASHINGTON (AP) _ Vice President Al Gore used his 50th birthday to promote volunteerism, working on a house in Washington's low-income Anacostia neighborhood with D.C. Habitat for Humanity.

Gore and his wife, Tipper, sweated to the tunes of the Rolling Stones, Steve Miller Band and the Beatles, joining forces in putting up drywall and windows while Gore staffers and Americorps volunteers hammered inside and lugged rocks from the house's future lawn.

Gore commented on a recent government audit, calling it a ``milestone'' and noted that ``right now we're inventing this house.''

The home's future owners have been approved, but they must pay 500 hours of ``sweat equity'' and $500 as a down payment before they are eligible to move in. Through the Habitat for Humanity program, they can buy the home through a no-interest 20- to 25-year mortgage.