The next version of Windows, code-named Longhorn, is still in the early stages of its journey to the retail corral, but ARN sister publication PC World’s hands-on look at a preview reveals features we'd love to have now - while raising some intriguing questions.

In addition to the interface revisions, including the new Sidebar, that we saw in our first glimpse of Longhorn, Microsoft has altered Windows Explorer, the program that controls the desktop and its computer- and file-browsing windows.

In our preview code (the official beta isn't due until the second half of 2004, and rumour has it that the upgrade may not ship until 2006), Windows Explorer routinely displayed much more information about files and computer resources than it does in Windows XP. New links in Explorer panels let users and/or applications associate search keywords, comments, and categories with files, data within files, or objects stored on other devices, computers, or networks. This is the first evidence of Longhorn's new WinFS file system, which lets you find related resources regardless of their physical location or object type.

Explorer's attractive displays of files and properties come courtesy of Longhorn's new graphics subsystem, code-named Avalon, which will hand much of its work to the PC's graphics subsystem.

Minimum requirements for the preview call for an 800-MHz Pentium III processor, 256MB of memory, and a graphics card with 32MB of video RAM. Such specs are beefier than XP requires, but Longhorn-capable systems should be commonplace by the time the OS ships.

Longhorn addresses some long-languishing Windows XP problems. The Internet Connection Firewall is on by default and has been upgraded to be bidirectional, stopping both incoming threats and any outgoing connections attempted by worms and Trojan horses.

Internet Explorer, meanwhile, at last includes a pop-up blocker just as every other Web browser in the world does, as well as plug-in and download managers and a convenient tracks-covering feature that clears all cache, cookie, history, and personal data. But Palladium security technology - now known as Next Generation Secure Computing Base (NGSCB) - isn't yet visible in the new OS.

Also new: Speech, a Windows XP Control Panel applet with no apparent purpose, in Longhorn contains an actual speech-recognition engine complete with training text. And a new User Accounts setting allows each user's appointments to display in the Login screen - but Longhorn so far lacks any bundled calendar software. This may simply be evidence of Longhorn's tighter linking with another upcoming Microsoft product: the next version of Office.

Longhorn may be a couple of years off, but Tablet PC users won't have to wait that long for an update. Microsoft plans to release a free upgrade, Windows XP Tablet PC Edition 2004, by mid-2004.

Code-named Lonestar, the upgrade focuses primarily on improving handwritten input. For example, when you place the pointer in a location that can take text (a document, browser address window, and so forth), the Text Input Panel - the window in which handwriting recognition takes place - will automatically appear as a small bubble that, when activated, will grow to its full size and appear close to the chosen text field instead of at the bottom of the display, as it does now.

Microsoft has also given the TIP context-recognition capabilities - for example, if you're filling in a browser address window, the TIP will be more likely to recognise a URL as such. You'll also be able to catch and fix mistakes in the TIP before sending text to an application.

New development tools will allow creators of third-party applications to incorporate some of the operating system's new functionality into their software. Meanwhile, the beta of the upgrade is due in early 2004, with final code to follow sometime this spring.