Michael Dell has failed to turn around market share losses since his return in January 2007. Dell's market share slipped to 13.6 percent of global unit PC sales in the third quarter of this year, from 16.1 percent in the third quarter of 2006, according to market researcher Gartner. Meanwhile, HP's third-quarter share climbed to 18.4 percent from 16.3 percent two years earlier. During the same period Acer Inc more than doubled its share to 12.5 percent, making it the No. 3 PC maker. Lenovo Group Ltd's share has dropped to 7.3 percent from 7.5 percent, putting it in fourth place. BACK TO CENTER Dell will centralize a far-flung global organization responsible for sales of its business products, which include personal computers, servers and storage equipment. The three new segments will supervise Dell's business with large corporations, government agencies, and small to mid-sized companies.