Microsoft executive Steve Ballmer went on the offensive against Apple in a recent interview, stating that Windows has gained market share on OS X, and that the browser Safari is a "rounding error."

In the third part of an interview with TechCrunch, Ballmer said that he believes the higher price of Mac hardware has turned away some consumers. He said the lower price of Windows 7 is meant to meet the current economic climate.

"Weâre gaining share. Apple is expensive," Ballmer said. "And in tough economic environment, people get it. Their model is, by definition, expensive. And weâve actually held or maybe even gained just a tiny bit of share relative to the Mac in the last 12 months. And itâs not really Snow Leopard. Itâs really Windows PCs versus Mac."

Since the debut of new MacBook Pros with cheaper prices this summer, Apple has seen its sales grow, while the rest of the PC industry has shrunk. In July, Apple was the fourth-largest computer maker in the U.S. Mac sales are expected to continue to expand in the just-concluded September quarter.

And at $29, Snow Leopard, Apple's new operating system, comes at a much cheaper price than Windows 7. Initial sales figures showed that OS has had sales twice as high as Leopard and four times better than Tiger.

However, earlier this year, Mac sales were relatively flat before new products were released. And the popularity of netbooks has been a growing market for PC makers. In his interview, Ballmer said that netbooks are "just the first battleground."

Another fight for Microsoft lies in the world of browsers, where Firefox has made significant inroads on Internet Explorer. Ballmer acknowledged the success that Firefox has had, but also took the opportunity to discredit the market share of Google Chrome and Apple's Safari.

"The most successful by far is Firefox," he said. "Chrome is a rounding error to date. Safari is a rounding error to date. But Firefox is not."

The Microsoft chief executive used similar language in July, when he told financial analysts that the rate of Mac adoption is statistically insignificant. He said quarter-to-quarter market share changes between Windows and OS X amount to a "rounding error."