LAS VEGAS—Microsoft's CEO Steve Ballmer on Monday evening delivered his company's final keynote at the annual Consumer Electronics Show in Las Vegas. Microsoft, which has occupied a large chunk of the CES exhibit floor for years, announced last month that 2012 would be its last year of participating in CES.

Microsoft has decided that it will make future product announcements at times it deems appropriate and not around the industry trade show's schedule.

Monday night's pre-show keynote, which was hosted by Ryan Seacrest, started off with a light-hearted look back at Microsoft's CES appearances over the years with a short video montage that mashed together highlights from Ballmer and former CEO Bill Gates' past keynotes.

From there, Seacrest and Ballmer guided the audience through a series of in-depth demonstrations of Microsoft's most recent product launches, including the latest PC operating system Windows 8, as well as the Windows Phone 7 (WP7) mobile platform.

Windows 8 and WP7 share various traits, including a similar user interface that Ballmer called the "Metro" environment, which consists of a frenetic home screen of live tiles and apps. The two platforms blur the lines between PCs, tablets and smartphones. Windows 8 users will be able to purchase apps from the Windows Store and run them on their Windows 8-based tablets.

At a press conference earlier today, Nokia unveiled the LTE-capable WP7 Nokia Lumia 900, which will launch in the next few months exclusively on AT&T's network. T-Mobile USA will launch the mid-range Nokia Lumia 710 on Jan. 11.

On the Xbox front, Ballmer said the company now has 40 million active users of the online gaming community. He also said that Microsoft has sold over 18 million Kinect sensors.

Microsoft is working to make the Xbox the center of the home entertainment system. The company announced content partnerships with Fox News, Verizon's FiOS and AT&T's uVerse, among others. Also demonstrated was a kind of interactive television viewing experience. Specifically, users will be able to use the Kinect sensor to actually influence the decisions characters make in a given program.

Ballmer said the Kinect sensor soon will be compatible with Windows machines. He said the company is now working with a variety of companies across industries to develop applications for Kinect for Windows.

Ultimately, Microsoft's final keynote revealed a company that has developed a mature ecosystem of devices and platforms that play nice together. As with Apple, apparently that means it's time to quit playing with the kids in the sandbox at CES.