Today sees the official launch of Microsoft's much vaunted operating system, Windows XP. For most of us this is hardly big news, as so much information about the product is already in the public domain, but from today you can do more than read about it, you can buy it and use it too.

Three PC World stores opened at midnight last night in order to make the first sales, although MD Simon Turner made no comment on how popular these events had been. However, with consumer preorders standing at 100,000 it looks as if plenty of people want to experience what XP has to offer.

Microsoft's chief executive Steve Ballmer says this is the "biggest thing we've done since [Windows] 95". Indeed, Microsoft expects the roll out of XP to be twice as successful as Windows 95, becoming "the new standard of the way people work".

Ballmer was candid about the failings of previous Microsoft operating systems, admitting that in the past customers have had to choose between reliability and compatibility. Professional operating systems such as NT and 2000 offered robust performance, but limited application support, while consumers suffered more frequent crashes but better software support with the likes of 98 and ME. XP aims to bring together these two strands providing both reliability and wide software support.

But XP is not the end of the road by any means. Ballmer said that there will probably be another operating system to take its place in a couple of years time. He also agreed with claims that users with older systems may have to upgrade in order to take advantage of the new operating system.

Microsoft has been battered by various storms of late, including a prolonged and difficult spat with the US government and the EC, accusations of dubious integrity in terms of the protection of privacy, allegations that it is continuing its anticompetitive actions by tying XP to various web services and companies, an inability to explain its international pricing and a general dislike of its new 'activation'-based licensing. This launch is just as important to the firm as 95 was.

See also our Special Report on XP.