Steven Sinofsky, Microsoft's head of Windows has announced that Windows 7 has been installed 670 million times.
He says that Windows 8 is "computing for the next billion people", and sees it as a shift from the old age of desktops to the age of touchscreens, smartphones, and social networking.
"Windows 8 is simply the best release of Windows ever," he said.
Microsoft today launched the new Windows 8 operating system and Surface tablet. Both devices go on sale at midnight tonight.
Microsoft used to be the world's biggest technology company. Its new tablet can't afford to fail if it wants to win back that title.