Much has been made about the fact that businesses most likely won't be in a hurry to upgrade to Windows Vista. But a report by Forrester Research suggests consumers won't stampede to purchase the new OS either.

Forrester analyst Ted Schadler said that customer households will adopt Vista much in the same way that they adopted Windows XP. This goes against the projections Microsoft has made that Vista will be adopted two times faster than any other Windows client operating system.

"Call us cautious, but we believe that most consumers will tread the path they've been on for years: they buy computers when the old ones break, when the prices come down far enough, or when a lifestyle event triggers the purchase," he wrote in the report. "And that means the best predictor of Windows Vista adoption is Windows XP."

It took more than four years for Windows XP to reach the majority of the PC install base, and it likely will take Vista the same amount of time, Schadler posits in the report, entitled 'A Forecast of Windows Consumer Adoption'.

Currently about 76 per cent of PC-owning US households are running a PC with some version of Windows XP. While he said that Windows Vista does have certain improvements in security and user interface, none of those "feels disruptive enough to trigger early purchases," he wrote.

"Therefore, the Windows Vista adoption pattern will look similar to the Windows XP adoption pattern," Schadler wrote.

In his report, Schadler predicted that about 12 million households will own Vista in 2007. This will grow to 73 million households by 2011.

To improve this rate of adoption of Vista, the report suggests that hardware vendors work with Microsoft to ensure that any PC purchased in the last quarter of the year be ready to run Windows Vista.

Schadler also suggested in the report that any customer willing to purchase a copy of Windows XP in December 2006 be offered a free upgrade to Windows Vista on 30 January, when the operating system will be generally available. Currently, some of Microsoft's hardware partners are offering free coupons for upgrades, but some coupons may require a fee, albeit a discounted one.

"Why should a consumer suffer just because the industry missed a shipping deadline?" Schadler wrote.

Forrester also suggests that Microsoft should ensure there are new applications for Vista that will provide substantial value-add and wow consumers if it wants them to upgrade more quickly.

Windows Vista was released to manufacturers on Wednesday, and will be available to business customers on 30 November. Microsoft is hosting a launch event that day in New York to mark not only Vista's release, but also the release of Office 2007 and Exchange Server 2007.