Windows XP users continued to put their old hoss OS out to pasture in April, statistics showed, but the now-unsupported operating system still powered more than one in every four personal computers on the planet. According to Web analytics company Net Applications, Windows XP dropped 1.6 percentage points in "user share," an estimate of the fraction of the world's computer owners that run a specific operating system, to end April with 26.1 percent of all desktop and notebook systems. It was the second consecutive month that XP shed significant user share.