Microsoft split up its Windows group earlier this year, putting some of the business into the unit that develops the Azure cloud and the rest into the group that works on Office and devices. It's all part of Microsoft's shift to focus on the cloud and artificial intelligence under Ballmer's successor, Satya Nadella.
Still, Windows is producing more and more revenue and a big chunk of profit, even as Nadella changes direction.
"I mean, this less importance on Windows thing I find a humorous thing by the press," Ballmer said in an interview on Monday at the WSJ Tech D.Live event in Laguna Beach, California.
Ballmer said he can't imagine the company would do anything to unwind it.
"If they were, I'd be selling," he said.
Windows revenue increased 5 percent to $19.5 billion in the latest fiscal year, which ended on June 30. That represents more than 17 percent of total revenue. Microsoft doesn't disclose operating income for Windows, but Ballmer said at the conference that the business accounts for $13 or $14 billion of operating profit. If true, that would represent about 40 percent of the total.
While Ballmer said he doesn't agree with how some of the changes at the company have been portratyed, he's generally bullish on the direction. Microsoft has released several apps for Android and iOS, and has sought to bring more content from phones into Windows.
"The company has made a smart choice, in my opinion, to go more platform independent," Ballmer said. In working across operating systems, "I think the company has done a good job," he said.
Ballmer has certainly been rewarded for hanging onto his stock. Since Nadella took over the top job in 2014, the stock has tripled and the company is now worth over $800 billion. Ballmer's net worth is estimated at over $40 billion, and almost all of that is from his current ownership in Microsoft.
"I'm glad we left the company with good profit streams and good technology," Ballmer said. "I'm glad Satya's taken that to whole new levels. I think that's fantastic, and as a shareholder, I think it's double and triple fantastic."