Like Michael Myers in the ‘Halloween' movie franchise (or the wasp of my nightmares) Windows XP refuses to go gently into the night. No matter how many times Microsoft sticks an axe into its recalcitrant head, XP just keeps on coming.

Recent reports suggest that Microsoft will allow PC makers to offer XP on new PCs until at least April 2010. And 96 percent of new netbooks - the fastest growing PC market - now ship with XP installed. Viva XP.

But why won't XP stick to the script?

Several reasons. Not the least of which is the failure of Windows Vista to win over PC users weaned on its predecessor. Vista is fine, but at launch it was oversold and undercooked. Microsoft's "most significant" OS had more shiny trinkets than XP, but was less stable.

Once word got around that Vista was far from perfect, the discerning user was always likely to stick with the XP comfort blanket. The more so given Vista's chronic, now cured, peripharel compatibility problems.

More importantly, Vista was punted out to users with existing systems that were never going to be up to the task. I use and like Windows Vista, but I wouldn't let it anywhere near a system with less than 2GB of RAM - despite Microsoft's early party line. Thus was another cohort of potential Vista evangelists once bitten, now made twice shy.

Modern mainstream computers are built to Vista's specification. But the success of low-spec, low-cost netbooks highlights one further reason for XP's bouncebackability. To today's digital natives, the most powerful, feature-rich product isn't necessarily the best. We live in a time of horses for courses computing - the right tools for the right job. In the age of the netbook, the 1GB PC is king.

For all that XP lacks some of Windows Vista's functionality and shine, it became the most popular piece of software in history by being fit for purpose. Functional, familiar, reliable. Able to run on almost any system.

Why won't Win XP die? Simple. It works.