According to W3 Schools, XP is installed on more than half the visitors to its site. http://www.w3schools.com/browsers/b...

Microsoft have said that it will keep extended support for XP going until April 2014, so about another three and a half years. http://support.microsoft.com/lifecy...

It's no surprise that nine years after it was released, XP is still top dog. Vista was released far too early because Microsoft were getting desperate in leaving it too long to have an XP successor. XP is now a fairly stable OS (at least within the Windows family), many drivers for hardware haven't been written for Win7 yet, and XP in comparison to Vista and Win7 doesn't have big hardware requirements. Then of course there's business suites who will have the cost of upgrading software and also hardware in some cases. XP is now in the position Win98 was about 5-6 years ago - Microsoft want to choke it off but knows it can't without risking the wrath of consumers of stopping the support of a popular product. Win7 will most likely overtake XP in the future in terms of usage, but it could take longer than Microsoft had hoped thanks to the financial situation in many markets and baring in mind that Win7 has now been commercially available for around two years already. Then Win7 will likely become the "new" XP, whose life cycle will probably go to at least 2020.

Actually if you look at the W3 Schools link and look at the percentage of visitors having Win98 over the last few years (baring in mind the demographic of the likely visitors of the site), particularly around the time "end of life" was announced, XP may well have some years left, in spite of a lack of new installs in the near future.