Britney Spears will open this year's Video Music Awards.The 25-year-old celebrity will perform "Gimme More," the first single from her upcoming album.Spears is a VMAs veteran: She covered the Rolling Stones' "Satisfaction" in 2000, stripping down to a nude-colored bikini top and matching pants; a year later, she performed "I'm A Slave 4 U" with a 7-foot albino python around her neck. In 2003, she and Madonna had the watercooler moment of the year with an open-mouth kiss -- in the opening act.Sunday's show in Las Vegas will mark Spears' latest -- and biggest -- comeback