One Laptop Per Child won't use Microsoft's Windows OS on its upcoming XO-3 tablet, which will run Linux, OLPC's CTO said Thursday.

OLPC's chairman Nicholas Negroponte last year said that the organization was "urging" Microsoft to make a full version of Windows available for the earlier XO-2, which was also based on the Arm processor. The XO-2 was later canceled.

The XO-3 will also use an Arm processor, but OLPC is ruling out loading multiple versions of Windows on the tablet, said Ed McNierney, OLPC's CTO, by e-mail Thursday.

"We have no evidence that Microsoft will make full-featured Windows 7 available on Arm, and that's their decision," McNierney said.

Arm processors can run the Windows Mobile OS, but Windows Phone 7, Microsoft's upcoming mobile OS, was also rejected by McNierney.

"Our XO tablet will be a full-function computing device, not a smartphone or a PDA. Windows Mobile was designed for those markets, not general-purpose computing, and it's just not useful to us," McNierney said.

Existing XO laptops, whose primary audience is children in developing countries, come with x86 chips and offer Linux and Windows operating systems. But OLPC and its partners like Sugar Labs have made progress in developing power-management features in Linux and that is the OS of choice for XO-3, McNierney said.

"Our ability to achieve our low power goals depends on being able to make appropriate changes throughout the operating system, and that's just not possible except in an open source environment," McNierney said.

An XO-3 prototype will first be displayed at the Consumer Electronics Show early next year running Google's Android OS, Negroponte said in an e-mail. By January 2012, XO-3 will likely run a different Linux OS.

Current XO laptops run Linux with the Sugar platform, which provides an education-specific user interface. Sugar development is being managed by Sugar Labs, a nonprofit organization. McNierney said the company plans to stick to Sugar, but developers will need to adapt it for multitouch input capabilities to conform with XO-3's tablet design. Developers may also need to come up with alternative desktop interface ideas, McNierney said.