Angiulo showed some prototype ARM devices running Windows 8, and said ARM processors will not be limited to tablets. "ARM enables ultra-portable computers of all form factors," Angiulo said.

Microsoft designed Windows 8 to meet the needs of a changing computer landscape, Angiulo said.

"The trends we're facing have changed," he said. "Today we're facing trends around immersive Internet computing, ultra-portable devices, and of course touchscreens. Windows 8 is a reimagining of Windows for those trends today."

Several top executives from ARM, Qualcomm and other chip vendors joined Microsoft for its press event. It had also showed the new OS a few hours earlier in the U.S., at the Wall Street Journal's D9 conference.

There was a slight shadow hanging over the event, after on Wednesday that said Microsoft is insisting its biggest chip making partners each work exclusively with one PC maker to help get the first Windows tablets to market quickly.