With a new CEO in place, Microsoft founder Bill Gates told CNBC on Monday he's excited about taking a more hands-on approach again at the software giant in "re-examining all its strategies."

Gates stood down as chairman in February, but remained a board member. He's now spending about a third of his time as a technology adviser to new Microsoft CEO Satya Nadella, who recently took over for the retiring Steve Ballmer.

"Satya is off to an amazing start," Gates said in a "Squawk Box" interview, following the weekend annual meeting of Berkshire Hathaway—of which he's a director. "[Nadella] drawing on a broad set of people in the company to get them rethink how can Microsoft move a bit faster."

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Sitting next to Berkshire's Warren Buffett and Charlie Munger in Omaha, Nebraska, Gates addressed a wide range of other topics, including the disclosure that he's .

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According to a filing with the Securities and Exchange Commission, Gates now owns about 330 million Microsoft shares after sales last week. That compares with Ballmer's more than 333 million, according to Thomson Reuters data.

"I sold for over a decade the same number of shares every quarter," Gates said. "That plan lasts through the end of this year. I'm going to retain a lot of Microsoft's stock."

Gates also talked about why he believes capitalism is a "fantastic thing" versus any other system. Making his case, he said the wealth of Buffett, Munger, and himself are "first-generation fortunes that show there is dynamism in this system."

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On the lighter side, Gates recalled the first time he met Buffett—telling the story about how his mom played an important role getting the two together.

Buffett said: "He was forced to meet me."

"It's actually true," Gates said. "My mom was having Kay Graham [of The Washington Post] and Warren over. And I was still sort of maniacal about not doing anything but working at Microsoft ... [but] I agreed to come by."

Gates said his reluctance to meet Buffett was rooted in his misconception that the Berkshire chairman and CEO was only interested in stocks and charts. He added that he was pleasantly surprised with the billionaire investor's thoughts on how to run corporations and building businesses.

For the past six years, Gates has mainly been focused on philanthropy at the Bill & Melinda Gates Foundation, which is largely funded by his Microsoft money.

—By CNBC's Matthew J. Belvedere. Reuters contributed to this report.