Worldwide PDA shipments totaled 3.4 million units in the first quarter of 2005, a 25 percent increase from the same period last year, according to Gartner, Inc. Microsoft Windows Mobile has become the No. 1 PDA operating system, as it accounted for 46 percent of worldwide shipments. RIM assumed the second position, as Palm OS slipped to the No. 3 ranking, due to Palm OS shipments declining 38.8 percent. Nokia in the fourth place.