New Windows-powered tablet or slate devices -- small, hand-held, wireless computers -- are in the pipeline from Acer Inc, Dell Inc, Samsung Electronics Co Ltd, Toshiba Corp, Sony Corp and a dozen other PC makers, Ballmer said at the company's annual partner conference in Washington, D.C., which was webcast.
"This year, one of the most important things that we will do in the smart device category is really push forward with Windows 7-based slates," said Ballmer. "This is a terribly important area for us."
Apple's iPad, launched in April, has already sold more than 2 million units worldwide, and threatens to take customers away from Microsoft-dominated desktop computing.
Ballmer did not mention Hewlett-Packard Co, the world's No. 1 PC maker, which has said it plans to build slate devices running the operating system devised by Palm Inc, which HP bought this year. However, HP's logo did appear on a slide listing PC makers working on slates which was displayed as Ballmer spoke.
At the same conference, Microsoft announced that online auction firm eBay Inc, tech services company Fujitsu Ltd and PC maker Dell are among the companies testing Microsoft's new Windows Azure platform appliance, which lets customers implement Microsoft's newest "cloud" server technology in its own data centers.
Microsoft is heavily emphasizing "cloud" services at the conference, essentially helping companies manage their data and computing power -- and those of their customers -- over the Internet.
Microsoft shares were up almost 2 percent at $24.75 on Nasdaq.