Microsoft has sold 350M copies of Windows 7

More than 350 million copies of Windows 7 have been sold, Microsoft reported Friday.

The operating system launched 18 months ago.

Its biggest competition on the PC is not the much maligned Windows Vista or Macs, but Windows XP.

To encourage people to upgrade from XP to Windows 7, Microsoft has stopped building some of its newest software to run on XP. For instance, Internet Explorer 9, Microsoft's new browser, runs only on Windows Vista and Windows 7.

It seems Windows 7 is starting to make inroads. Earlier this month, research firm StatCounter said Windows 7 had passed Windows XP in market share in the U.S.

Here is Microsoft's blog item on the milestone.

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