Microsoft expects 350 million devices running its Windows 7 software to be shipped globally this year as it prepares the next version of the operating system to challenge Apple's dominance in tablet computers.

"It makes Windows the most popular single system," Steve Ballmer, chief executive officer of Microsoft said today.

Corporate demand for programs including Windows 7 helped Microsoft report third-quarter profit last month that exceeded estimates. The company is working on Windows 8, the newest version of the operating system that can be used in touch-screen devices, to help win back consumers and narrow Apple's lead in the market for tablet computers.

Microsoft will finish work on Windows 8 this summer and put it on sale around October, people with knowledge of the matter said in March.

The release of Windows 8 and demand for ultrabooks and other thin notebooks should drive personal-computer sales in the second half of this year, after modest shipment growth in the first six months, IDC said in March.

Global PC shipments will rise 5 per cent in 2012 after gaining 1.8 per cent last year, the market researcher said.

More than 103 million tablet devices will be sold in 2012, with sales tripling to 326.3 million in 2015, according to Gartner. Apple is set to account for two-thirds of the market in 2012, Gartner estimates. The company's share will drop to 46 per cent by 2015, while Microsoft's will climb to 11 per cent.

Apple introduced the third-generation iPad in March, raising pressure on Microsoft to recover sales lost to the Apple device and revitalise slowing PC sales.

Bloomberg