Windows XP is the operating system release that unifies the Microsoft range, with all the desktop versions now built on the NT/2000 code base rather than the shakier foundation of Windows 95, 98, and Me. That makes XP a great upgrade for users of the now-obsolete 9x and Me line, but for those already on Windows 2000 Professional it is a closer call. Despite the similar name, there is no special synergy between Windows XP and Office XP, which works fine on Windows 2000.

XP certainly looks different, with rounded window corners, larger and more detailed icons, and a clean-look desktop that on first installation shows only the taskbar and Recycle Bin. XP is also more customizable than earlier versions of Windows, and includes visual themes that let you change the whole appearance of Windows in an instant. That is the window-dressing, but underneath are some significant improvements. One of the most interesting is Remote Desktop. A standard XP feature, this uses technology from Microsoft Terminal Server to enable users to access their computer over any connection; for example, by dialing into the office from home. This is not just file access--this technology lets you run applications remotely as if you were sitting at your desk at work. This is mature technology, stable and carefully thought out. So, for example, you can print from a remote word processor to a local printer. A variation on the theme is Remote Assistance, where the user can allow a remote helper to view their desktop, or optionally gain control of the keyboard and mouse, in order to troubleshoot a problem. The feature can also be disabled to ease security concerns.

Laptop users benefit from enhanced power management, with options to extend battery life by reducing CPU speed and display brightness. IrDA support has been fixed so that, unlike Windows 2000, Windows XP can easily use modems in mobile telephones via infrared. A new screen font, ClearType, improves legibility for laptop or other flat screens, and there is built-in support for wireless networking using the popular 802.11 standard. A great feature of XP, also found in Windows 2000, is the ability to synchronize network files with offline copies. Previously, these files could not be stored securely, but now they can be encrypted.

For Web browsing, XP comes with Internet Explorer 6.0. The enhancements in IE 6.0 are mainly of interest to Web developers, and in any case Microsoft makes IE freely available to all Windows users. Although Java is not installed by default, it is not difficult to download a Java Virtual Machine (JVM). Windows Messenger, originally a chat client, has evolved into a collaboration tool that allows for video conferencing and application sharing.

The most significant new feature for Internet users is the built-in firewall. A firewall protects against one of the most disturbing security risks, in which other users unknown to you might connect to your computer while it is online, reading private files or causing other damage. XP's built-in firewall is a simple affair, but it does prevent most types of unauthorized connection.

Windows XP has strong multimedia features. The new Media Player lets you copy music from CD to hard disk, create your own playlist, and write your own music CDs if you have a CD writer. Although there is loss of quality as a result of compression, the process is easy and convenient. Media Player 8.0 can play back DVD video, but only if a hardware or software DVD decoder is already installed. You can also play MP3 audio files and MPEG videos, but sadly, not the popular RealMedia formats. In the end, Media Player does nothing that you cannot also do with free alternatives, but it is slick and nicely integrated.

The XP user interface is not a radical departure from earlier versions of Windows, but there are a number of small changes that together add up to a significant improvement. The Start menu now automatically features the most frequently used programs at the top of the list, and you can add and remove shortcuts by right-clicking the icon and selecting Pin or Unpin from the pop-up menu. Windows online help is integrated into a Help and Support Center that works like an internal Web site, with searchable help, tutorials, and walk-throughs.

Windows XP Professional includes all the features of Windows XP Home, and adds support for dual processors, encryptable file systems, offline folders, the Remote Desktop as described above, and extra administration features that come into play when connected to a Windows server domain. XP is demanding on hardware, and it would be a mistake to install it on less than Microsoft's recommended minimum requirements. There is also activation to consider, a mildly annoying anti-piracy measure that requires you to obtain a code from Microsoft for full installation, and in the future if you reinstall or make major system changes.

Overall, it's a big step forward for those coming from Windows 9x or Me, and attractive rather than compelling as an upgrade from 2000.