Companies should think twice about skipping Windows Vista and should get started sooner rather than later on updating their client desktops to the latest Microsoft operating system, according to an independent report issued by Forrester Research.

The report, "Building the Business Case for Windows Vista," says there are a number of reasons to upgrade now, even if avoiding Vista to wait for Windows 7 may seem like a viable option. The company has issued a second report, "Lessons Learned from Early Adopters of Windows Vista," to show how some users have handled migrations.

Forrester lays out five reasons companies should begin upgrading soon, including the fact that there are few viable alternatives, given the depth of Windows penetration in the enterprise. The research firm says its hardware surveys show Windows is the operating system found on 99% of PCs in North America and Europe. In addition, Windows is the operating system on 97% of PCs in small businesses, Forrester says.

Benjamin Gray, author of the report, notes that while Apple's Mac OS and Linux are enjoying renewed visibility, switching thousands of users from Windows to another platform is not a workable solution for the majority of companies. In addition, users need to stay current on Microsoft and independent-software-vendor (ISV) support of Windows operating systems, he says.

Forrester notes the expiration milestones for extended support and security patches on Windows 2000 and XP, and the fact that Windows 7 isn't expected to ship until 2010 at the earliest, as reasons users should keep their desktop operating system fresh.

Two other reasons for a prompt migration to Vista are the probable unavailability of Windows XP after June 30, 2008, and uncertainty around Windows 7. Microsoft has extended the deadline once for XP already, and Forrester predicts it will not happen again. In addition, the report says uncertainty around the availability and feature set of Windows 7 is a red flag for those looking to skip Vista.

Finally, the report says that Vista has valuable features and functions, such as security and user enhancements, citing the opinions of early adopters Forrester surveyed. The firm says these early adopters also reported on their overall migration experience, confirming that compatibility issues are still their No. 1 headache. Nevertheless, they reported they found workarounds for most of their issues, according to the survey.

Forrester recommends that users tie upgrades to PC refresh cycles, make sure desktops have 2GB of memory and limit upgrades to PCs that are less than 18 months old. Companies also should use the Windows Vista Hardware Assessment tools, which are free from Microsoft, and use stopgap measures, such as client and application virtualization, in the short term. They also should press their ISVs for Vista compatibility.