Microsoft's Steve Ballmer Reveals His Biggest Regret Microsoft CEO Steve Ballmer has directed the sprawling company for more than a decade, overseeing both successful and botched acquisitions while pushing the firm into new markets. As Microsoft braces for the announcement of his successor, the 57-year-old recalled the decisions that have both helped and hindered the U.S. software giant. "I do think we're far more focused than we were when I took over," Ballmer told Fortune. And that's partly a function of the time. We've gone from being a complete leader to a leader and a challenger, both in the same body. And when you're a challenger, you do have to pick and choose and be more focused. Ballmer, who took the CEO reins from Microsoft co-founder Bill Gates in 1998, is known for his role in the successful development of the Xbox gaming console. Even as the company was forced to take a $1 billion write-off on the first generation of the glitch-ridden system in 2008, Ballmer continued to champion the project, according former Xbox division head Robbie Bach. The Washington state-based company announced Wednesday it sold more than 2 million Xbox One systems in just 18 days since its release, breaking a new company record. His legacy, however, is equally marred by his missteps, including Microsoft's $6 billion purchase of online ad firm aQuantive in 2007 that led to a $6.2 billion write-down five years later. Ballmer has also acknowledged the acquisition of Longhorn, as a part of a poorly planned rollout of the Windows Vista operating system, was a flop. But he contends Microsoft has seen success in plenty of acquisitions. "The aQuantive acquisition? Obviously not a good acquisition. But in the company we were, it's about acquiring in addition to managing costs and getting price. And we have been very good at that. "In the last five years, probably Apple has made more money than we have," Ballmer went on to tell Fortune. But in the last 13 years, I bet we've made more money than almost anybody on the planet. And that, frankly, is a great source of pride to me. For the entire interview, read Fortune's story.