Software incompatibility, the need for hardware upgrades, and comfort with existing versions of Microsoft Windows are all causing businesses that once planned to roll out Windows Vista as fast as consumers to put off their deployments, according to Forrester Research.

According to a report published last week and publicly released on Tuesday, Forrester says "most" of the 45 IT managers it spoke to this spring are waiting for the release of Vista Service Pack 1 early next year before starting to "seriously consider" upgrading to Vista. Many others also cited the late-summer release of System Center Configuration Manager 2007, the upgrade to the deployment software formerly known as Systems Management Server, as another reason they have not started to move from Windows 2000 or XP to Vista.

The informal survey, conducted by Forrester analyst Ben Gray, follows upon a more quantitative survey of 1,605 IT managers in North America and Europe, conducted by Forrester in May 2006. In that survey, 31 percent of respondents said they planned to deploy Vista within the first year of release with 53 percent saying they planned to upgrade within the first two years.

Those "fairly aggressive" deployment plans, however, failed to materialize because of both "the intricacies of running such large, complex, and distributed corporate environments" and "wariness," Gray wrote.

"Many of the IT pros we've spoken with feel like they've just completed their OS migration project and are wary of starting a new one anytime soon," Gray wrote.

Forrester's data, while mostly anecdotal, is further evidence that while Vista appears to be doing fine among consumers and SMBs with more than 60 million units shipped as of last month, big business is mostly saying no.

That 60 million figure above excludes volume licenses, and Microsoft says it does not track how many of its Windows volume license customers have upgraded to Vista -- something they could do at any time.

Another reason for the Vista delay is the operating system's limited compatibility with existing applications. According to Gray, IT pros who were interviewed said compatibility ranged from 60 to 90 percent for their existing software.

Finally, users are waiting for Configuration Manager to aid in deploying Vista despite the fact that Microsoft is pushing its Business Desktop Deployment offering as the tool for facilitating that process.

The delay is happening in spite of the fact that the 45 IT pros Gray interviewed this year say Vista offers attractions like better security through its User Account Control and BitLocker Drive Encryption and better performance through features like Aero and SuperFetch.

While few are thinking of moving off of Windows, according to Gray, some are thinking about holding off on Vista until the end of Microsoft support for XP and 2000 forces them to upgrade, wrote Gray. Regular support for Windows XP concludes in April 2009; extended support for Windows 2000 ends in July 2010.

Others will start moving with the arrival of SP1, which Gray expects will include more drivers for peripherals, better security, and software updates for better administration and performance. One big change, a court-mandated order to let users turn off Vista's built-in desktop search engine in favor of a third-party tool, such as Google Desktop, might not be ready for SP1, Gray wrote. Nor should users expect features like the WinFS storage subsystem.

Like other research firms, such as Gartner, Forrester recommends that companies start planning for Vista now. The consultancy also recommends that businesses start their pilot programs on laptops because those devices are refreshed more frequently and need BitLocker more urgently than desktop PCs do.