Today is a very important day for Microsoft: it's the first day that Windows XP can no longer be bundled on new PCs and it's also the first anniversary of the release of Windows 7. Either Microsoft planned for these dates to coincide, or we just have a big coincidence on our hands.

Due to Vista's performance issues on cheap netbooks, Microsoft had to extend the Windows XP installation deadline for its OEM partners. Back in 2008, Microsoft told OEMs that October 22, 2010 would be the last day they could sell computers that come with Windows XP.

XP was first released to retail channels on October 25, 2001. In recent years, the OS has become a thorn in Microsoft's side as the company tries to push the operating system's successors. Despite its outdated security systems and other issues related to being a nine-year old OS, many users still cling to it due to familiarity. In fact, it's still the most popular operating system in terms of market share.

In related news, Windows 7 turns one today. Despite XP's popularity, it has been growing the fastest of any operating system to date. In its first year it has already sold 240 million licenses. Microsoft hopes to push more users to it with releases that use hardware acceleration only available on Windows Vista and Windows 7. So far, these include Windows Live Essentials 2011 and Internet Explorer 9, neither of which can be installed on Windows XP.