Even when Windows 7 launched into a warm reception (and brisk sales), Microsoft didn't reveal exact sale numbers for its new OS – until today.

Microsoft CFO Peter Klein announced at the Morgan Stanley Technology, Media & Telecom Conference that Windows 7 has sold 90 million licenses to-date.

Up until recently, Microsoft's company line when boasting about Windows 7 sales is that is the fastest selling operating system in history, but without any accompanying number.

This news comes just days after the expiration of the free use of Windows 7 Release Candidate.