Helped by publicity generated by its inclusion among the five films nominated for a best-film Oscar, the DVD for the Johnny Cash biopic Walk the Line has quickly become the top-selling video of the week. Twentieth Century Fox Home Entertainment said Wednesday that the DVD sold more than 3 million copies on Feb. 28, its first day on the shelves. "We're thrilled with this sales velocity and expect all of the activity around the Oscars to further boost sales and awareness this week and well into next," company spokesman Steve Feldstein said.