In a rousing opening keynote for its Build 2014 conference here in San Francisco on Wednesday, a series of Microsoft executives pulled out all the stops, announcing new products, upcoming initiatives, and some amazing giveaways for show-goers. But as the keynote edged into its third hour, the firm finally delivered the news everyone had been waiting for: It will indeed bring an evolved Start menu back to Windows and let users run Modern mobile apps in floating windows on the desktop.

"Our commitment is to make Windows more personal and accessible to individuals, and to ensure a vibrant ecosystem through closer collaboration with our industry partners," Microsoft executive vice president Terry Myerson said. "The news today shines a light on continued Windows innovation in ways that benefit our customers, partners and developers alike."

And there was a lot of news.

Microsoft started off the show by highlighting Windows Phone 8.1, a major release of its smart phone operating system that adds important new features like the Cortana voice control software, a notification center called Action Center, and many new customization capabilities. Cortana was the clear hit of the show, offering dramatic improvements over rival systems like Apple Siri and Google Now, including deep integration with popular third party apps. You can learn more about this coming update in my Windows Phone 8.1 Preview, but the first new handsets with this OS version will ship in the coming months and all Windows Phone 8-based handsets will get the update for free by the end of the summer.

The firm next moved into Windows 8.1 Update 1, which will ship for free to all Windows 8.1 users next Tuesday as part of Patch Tuesday. (MSDN and TechNet subscribers can download this update now.) Update 1 takes major steps towards making the Modern mobile experiences in the OS more accessible to traditional PC users with a mouse, and takes Windows into new, low-end devices with just 1 GB of RAM and 16 GB of storage. You can find out more in my Windows 8.1 Update 1 Review.

In its first real nod to developers, Microsoft revealed that it will let developers create universal apps that can run on Windows 8.1, Windows Phone 8.1 and—it announced later in the show—on Xbox One. These universal apps are really multi-project solutions in Visual Studio, in which the eventual apps for each platform can share much more code then was possible in the past. That's because all three platforms will now support a new version of the Windows Runtime that debuted in Windows 8. (Xbox One support for universal apps is coming sometime in the next year.)

Microsoft also revealed that it will help developers overcome what is now one of the weaker areas of the Windows app ecosystem: Using this new universal app infrastructure, developers will be able to sell an app to users from one platform and then give them free access to the same app on the others. There will be a new "Made for Windows Phones and Windows PCs" logo program built around this and related universal capabilities.

Next, the firm provided a real demonstration of an early version of Office "Touch" for Windows, which will be a universal app suite that runs on both Windows 8.1 and Windows Phone 8.1. We only got a peek at PowerPoint, but it was indeed more powerful and feature-rich than the version Microsoft recently released for iPad, which should quell some complaints. No word on a release date, but you can find out more about this in Office "Touch" for Windows to Outclass Version for iPad.

Finally, Microsoft confirmed the news I had exclusively reported in Further Changes Coming in Windows "Threshold": it will make a new Start menu available as an option and will allow users to run Modern mobile apps in floating windows on the desktop. This announcement was deliberately worded—Myerson said only that it would come in "an update to Windows 8.1"—but my sources confirmed that it was still part of "Threshold," which will most likely be called Windows 9. On the record, several Microsoft executives confirmed Wednesday after the keynote that the timing and delivery method for this update were deliberately left vague because either could change.

Then the firm delivered another blockbuster: It will now license Windows and Windows Phone to hardware makers for free for use with devices that have screen sizes under 9 inches. That's all phones, of course, but it's also the volume part of the tablet market.

With the crowd still swooning, the firm revealed that all Build attendees would receive a free Xbox One, which they can pick up at the show, and a $500 gift card for the Microsoft Store so they can buy the device or software of their choice.

Outgoing Nokia executive Stephen Elop then announced three new Windows Phone handsets, the Nokia Lumia 930—a high-end device for international markets that is very similar to the Lumia Icon sold here in the US; check out my Nokia Lumia 930 Preview for details—and the low-end Lumia 630 and 635, both of which will be sold around the globe and cost under $200. He was followed up by new CEO Satya Nadella, who provided a surprisingly robotic "virtual Q & A" with prerecorded (and no doubt heavily vetted) questions.

Nadella's appearance was a surprising lull for an otherwise impressive showing, and it will be interesting to see how Microsoft follows it all today with the day 2 keynote. In the meantime, I've got a bunch of other stuff to post about universal apps, Cortana, free Windows, and some other Nokia devices. It's going to be a busy week.