Despite its many faults and niggling flaws, there's no denying Windows XP is good enough for most users. It's sufficiently capable, stable and secure, and there are no risks of incompatibility with the hardware or software already on the market.

It doesn't help that several key components of Vista, including the new Internet Explorer 7 web browser, Windows Media Player 11, Windows Defender spyware smasher and the Windows Desktop Search engine, are available as a free downloads for Windows XP. This gives users even more reason to stick with their current operating system rather than risk the relative pain and undeniable expense of an upgrade.

Of course, Vista has plenty left in its quiver. There are new programs such as Windows Photo Gallery, with solid capabilities for organising and editing digital snaps, tools for turning home movies into DVDs and even a simple desktop calendar. (If you think these are Microsoft's answers to the Mac's iPhoto, iMovie and Calendar, you're not far wrong.)

XP users can run the new Windows Desktop search engine but in Vista it's more tightly integrated into the operating system. Vista's user interface is more finely tuned, especially for working with digital photos, music and video, along with beefed-up security, a streamlined desktop and oodles of visual effects to bolster the wow factor.

Most crucially, Vista is about more than individual applications. It's about the evolution of the Windows operating system and a better "experience" with the personal computer by being more than the sum of its many parts.

"The way people use computers has substantially changed over the five years since we released Windows XP, PCs are now where people store their digital photos but five years ago digital photography was still in its infancy. These days it's totally mainstream and people view, edit, print and email their photos. It's the same for music. Now people have all their music sitting on the PC.

"Those two simple things, photos and music - and of course the impact of the internet, especially with broadband - have transformed the way people use computers at home. In the past, people who had a PC at home needed it for work or they were computer enthusiasts. Now there's a true 'home user' scenario.

Shiny boxes of Vista will be stacked high at retailers from tomorrow but there's unlikely to be a rush of people upgrading their existing PCs from XP to Vista. The new operating system makes hefty demands on a PC and despite Vista's long gestation period and widespread testing there are still many compatibility issues with other software and hardware.

This means the best path for Vista will be from people buying a new PC, especially given Vista's ability to tap into the power of modern graphics chips to speed up not just the display but a system's overall performance. Icon recommends any Vista-class PC will need at least 1GB of RAM and should run a dual-core processor, ideally one from Intel's Core 2 family.