Now things have changed somewhat, mainly thanks to Linus (pronounced Linn-us) Torvalds who created Linux. The Linux phenomenon has grown exponentially in the intervening years and, since round 1998 when the big computer manufacturers started taking it seriously, has become very popular. The biggest difference between Microsoft Windows and Linux is the licensing model that each uses.

This licence does not mean that you own the operating system. All it does is give you the right to use it as specified in the licence. Many people are surprised to discover that the Windows licence does not give them the right to install the operating system on another PC - even if they wipe it off the PC it originally came with.

The Linux operating system is based on the GNU Public Licence, which has many peculiar features. The GNU Public licence says that you not only have the right to install and run the software on as many PCs as you want and even make copies to pass on to other people (so long as you include a copy of the GNU licence), but it also means you have access to the source code.

For many people, access to the source code is academic: you cannot do anything with it unless you understand programming languages. You can compile it to run on your machine, but the boxed product is already compiled anyway and ready to run. But theoretical access to the source code is important because this is how programmers all over the world are able to help debug, tweak and improve the code.

Windows XP also benefits from - or suffers, depending on your feelings about simple primary colours - a redesigned user interface. Those who don't like the new look can always choose to switch to the 'classic' Windows interface. But however you look at it, the operating system has been praised for its ease of use and it represents the most stable system Microsoft has produced - stability long overdue, many believe.

Windows XP also features improved support for multimedia - with a beefed up Windows Media player and the integration of Internet Explorer 6, there is also Windows Movie Maker, a simple digital editing application. It also comes with integrated Roxio CD-burning software, and Microsoft's Windows Messenger, for instant messaging.

While the Home edition is aimed at consumers and the Professional edition at business users, this does not mean that small businesses should ignore the fully-featured - and cheaper - Home edition.

How do the two editions compare? Essentially, Windows XP Professional contains everything found in the Home Edition but adds certain system management features. For example, security issues are simplified in the Home edition - anyone logging on to a Home machine has full control over it. The Professional edition supports up to two processors in the machine, while Home only supports one. The professional Edition supports Remote Desktop - a single session version of Terminal Services. The Home edition has no backup utility. Professional supports EFS (Encryption File System) so that you can encrypt individual files or folders for local security. Other networking features not found in Home include SNMP, simple TCP/IP services and client services for NetWare, Network Monitor and the Multiple Roaming Feature.

Windows 2000 offers better security and more stability than you'll find in either Windows 98 or Windows ME, but lacks some of the multimedia enhancements that made it into Windows ME, such as Windows Media Player. Support for video and sound cards and joysticks is more restricted too in Windows 2000, making it unsuitable for game play.

Unix operating systems generally have reputations as being very robust, rarely requiring a reboot, and their multi-user nature means that you can set up a Unix operating system so that dozens and even hundreds of users can log into a machine. With Windows, you would have to buy one of the server versions to enable users to log on.