We were in San Francisco yesterday as Microsoft unveiled the latest beta of Internet Explorer 9 and, like many present, we were impressed. From everything we saw, it was all it was hyped up to be - visually stunning, fast and full-featured. Then came the one, big catch - it's only available for Windows 7.

The Register says that it got the official word from Microsoft and if Internet Explorer 9 is something you want, then Windows XP just isn't going to do.

According to The Register, Ryan Gavin, senior director of IE business and marketing, confirmed that "Microsoft would not put IE9 hardware acceleration features in the current version of its browser, IE8, or back port IE9 to older PCs running Windows XP."

For now, this means that more than half - around 55%% of computers, according to StatCounter - will be unable to run Microsoft's latest browser, but Windows 7 users are on the rise. Windows 7 debuted just over a year ago and has grabbed nearly a fifth of all computers on the Web in that time.

This isn't the first time that a browser has been released to exclude an old operating system and, in case you've forgotten, Windows XP (like its Internet Explorer 6 counterpart) is nearly a decade old. When Microsoft released Internet Explorer 7 in 2006, Windows 2000 was left out of the equation.

While we're disappointed, the abandoning of Windows XP seems reasonable given the numerous features that wouldn't work outside of Windows 7. Much of the talk yesterday around IE 9 was about moving the browser out of the way of the website, with features like "jump lists" and the "pinning" of websites to the desktop. These features, along with hardware acceleration using DirectX 10, would be unavailable on Windows XP. As Microsoft showed during a reviewers workshop yesterday, much of Internet Explorer 9 has been rebuilt from the ground up. If this means that we don't have to deal with the clunky IE of the past from now on, so be it. Our only lament is that a better, standards-based version of IE will never happen on XP, and for now, XP isn't going anywhere fast.

IE9 will, however, be available for Windows Vista. Show of hands - anyone still running Vista?