Windows XP's upcoming end-of-life means that some 200 million PCs will need upgrading or replacing.
That's according to Microsoft reps, speaking at the Microsoft Worldwide Partner Conference keynote in Los Angeles this week and writing on the Windows team blog.
Windows XP was removed from retail channels three years ago. It remained available through OEM channels rather longer though, and is still available as a 'downgrade' from Windows 7 for users unwilling to migrate to the newer version.
However, Microsoft says it will stop providing security fixes, updates and online tech support for the 10 year-old operating system on 8 April 2014.
For those determined to stay with Windows, the length of time needed to do large roll-outs means that the deathknell even though it is almost three years away is a call to action.
In a Gartner report last year analysts Michael A Silver and Stephen Kleynhans suggested that organisations planning to deploy Windows 7 needed to get XP out well before support ends, ideally by 2012 and certainly by mid 2013.
But XP's replacement does not have to be another Windows PC, of course. As well as alternative desktop operating systems Mac OSX and Linux, most obviously there are plenty of other ways to deliver information and applications to users, as Ovum principal analyst Richard Edwards noted.
"Most businesses and institutions gave Windows Vista a wide-berth because of technical and compatibility issues, and so Windows 7 has quickly become the operating system of choice for new PC deployments," Edwards said.
"But with sales of tablet and thin-client computing devices growing rapidly, and alternative application delivery architectures starting to take hold, we believe that by 2014 many organisations will have decided to adopt alternative end user computing models; thus making Windows XP the last major corporate version of the Windows desktop operating system."
