Initial sales of Windows 7, Microsoft's newest operating system, were "fantastic" in Japan and helped spur PC sales in the country, CEO Steve Ballmer said Thursday.

"We've had a great response here in Japan," he said at a Tokyo news conference. "Certainly we've seen initial sales be fantastic. The first ten days were bigger than the first ten days of XP or Vista or any other Windows launch that we have done."

Microsoft had strong support for the new operating system from Japanese corporate users and PC makers. Around 230 enterprises took part in the early adopter program that put Windows 7 in their hands before the public launch and roughly 670 new computers were launched to coincide with the new operating system.

As a result hardware sales experienced a double-digit jump thanks to Windows 7, said Ballmer.

"I think it's quite clear when you look at hardware sales, where we've seen an almost 20 percent growth year-over-year in the pace of hardware sales since the launching of Windows 7," he said.