By the end of 2007, less than 5% of installed PCs worldwide will sport some business-oriented version of Windows Vista, according to Gartner.

By comparison, 47% of PCs will likely be running Windows XP Professional, and nearly 10% of PCs will still be running Windows 2000 Professional, an operating system that will then be seven years old.

The percentage of PCs running a business flavour of Windows Vista is expected to rise to 15% by the end of 2008. But that will still be dwarfed by the 40% of installed PCs still running Windows XP Pro.

Given the hype around the operating system (OS) release yesterday – five years in the making – Microsoft officials likely wish that all companies were like Sasfin Bank. But business adoption is expected to only grow slowly over the next two years.

The Johannesburg-based, South African commercial bank plans to start upgrading to Windows Vista by March and have all of its 430 employees running the new OS by the end of 2007.

"We have a very spoiled user base," said Dawie Olivier, Sasfin's project manager for information technology.

As part of Sasfin's normal three-year hardware refresh cycle, Olivier plans to bring in new PCs with Vista pre-installed. But he also plans to take the unusual step of retrofitting existing computers with more memory and faster video cards to handle Vista's beefed-up requirements. "We've decided it's not cost-effective for us to support multiple operating systems just because we're shy about cracking open a few PC cases," he said.

But most companies aren't likely to deviate from their normal routine - extensive pre-upgrade testing that can take more than a year, and staggered three-to-five-year cycles for replacing hardware, said Michael Silver, an analyst with Gartner.

"More than half of our clients are telling us that they're only bringing in Vista as part of their regular hardware refresh," Silver said. He expects many corporations next year to exercise the "downgrade rights" in their Software Assurance contracts with Microsoft. This move will let them order new PCs with Windows XP Professional, which they can upgrade to Vista in a few years when they are truly ready to move.

As a result, Gartner expects 22% of PCs sold next year to come with Windows XP Professional. Most companies won't start moving towards Vista until 2008, when 52% of new PCs worldwide are expected to ship with a business version of the OS, according to Gartner.

The installed base will continue to lag, though. Only by the end of 2009 will the numbers of PCs running a business version of Vista equal those running Windows XP Professional.

In addition to companies unwilling to budge from their standard PC upgrade cycle, it seems most are loathed to tinker with existing hardware, no matter what total cost of ownership (TCO) savings Microsoft promises.