Ballmer's back: Former Microsoft CEO works crowd at Oxford

Ballmer's back: Former MSFT CEO speaks at Oxford

Steve Ballmer still knows how to work a crowd.

The former Microsoft CEO made his first public appearance Tuesday after leaving the helm of the tech giant, delivering a speech to graduate students at Oxford University on his retirement and the future of his former company.

Still serving as a board member at Microsoft after current CEO Satya Nadella succeeded him, Ballmer made a candid concession to his former chief rival.

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"Empowering technology for all, that ought to be a brand proposition that if we run a company correctly can last 20, 30, 50 years or more," Ballmer said during the speech.

"I had a bunch of guys at Microsoft—we were going through angst five or six years ago. People were talking about 'Oh, what do we want our brand to stand for?' Let's face it, Apple has had a good run recently and Apple is quote, cool, unquote."

"Unquote, quote? You're choice," Ballmer added, drawing laughs from the crowd.

Ballmer also revealed to the crowd his biggest regret during his tenure at Microsoft, according to The New York Times. The company should have integrated hardware and software sooner, he said.

—By CNBC's Jeff Morganteen. Follow him on Twitter at @jmorganteen and get the latest stories from "Squawk on the Street."