In a sure sign that many companies are far from eager to upgrade to Windows Vista, analyst firm Forrester Research has published a report urging enterprises not to wait for Windows 7.

"Although we applaud companies for thinking ahead, there are some harsh realities for those considering skipping Windows Vista," said Forrester analyst Benjamin Gray in the report.

Forrester outlined the perils of holding out for Windows 7, the next version of the Microsoft operating system expected some time in 2010.

"Ironically, one of Microsoft's biggest weaknesses - the unpredictable release schedule of its desktop operating systems - will likely spur adoption of Vista as a result of this lack of faith in Microsoft delivering Windows 7 on time," said Gray.

The arrival of Vista Service Pack 1, and Microsoft's decision to phase out XP on new PCs from 1 July, are compelling reasons for companies to upgrade to Vista, according to Gray.

The analyst also trotted out Vista's oft cited benefits including improved administrative tools, security tools like User Account Control and integrated search functionality.

The report pointed to negative press coverage for Vista and a lack of early adopter case studies for the reluctance of CIOs to embrace the new OS.

"Because adoption has been cautious, it has been a challenge for companies to learn from early adopters," said Gray.

The report follows a Gartner study last summer which also urged companies not to wait for Windows 7, pointing out Microsoft's reputation for slipped launch deadlines and a general lack of detail surrounding technical requirements for the OS.

• Forrester Research Report: Building The Business Case For Windows Vista: Five Reasons to Start Your Migration Soon