Windows 8 will be released to manufacturing the first week of August, and the first PCs running the operating system will go on sale in late October, Microsoft confirmed today.

The timing is not a surprise. It's within the range of what we expected given the availability of a Release Preview in late May.

Windows 8 has been the most tested prerelease operating system of all time, Microsoft VP Tami Reller said on stage at the company's Worldwide Partner Conference in Toronto. In addition to hardware running Windows 8 going on sale in late October, customers will be able to upgrade from Windows XP, Vista, or Windows 7 for just $39.99.

For the first time, Microsoft is planning to build its own tablets, with an ARM-based Surface device planned for availability at around the time Windows 8 launches. An Intel-based Windows 8 Surface tablet built by Microsoft will be available a few months after launch.

But today, the focus was on partners. Reller showed off many planned tablets, PCs, and Ultrabooks from partners such as HP, Lenovo, Samsung, and Acer. "We have engaged with the top OEMs on literally hundreds of device designs for Windows 8," Reller said.

The designs include tablets that convert easily to PCs, and a Lenovo all-in-one PC with a traditionally sized monitor that accepts touch inputs. Reller demonstrated a painting program in which the user can actually use a brush to paint on the screen.

Microsoft also teased the next version of Office, but without providing any real details just yet. CEO Steve Ballmer said, "I'm running Office 15 and Windows 8 all day, every day. I'm completely in love."