In our recent Research Note, "Ten Reasons You Should and Shouldn't Care About Microsoft's Windows Vista Client," we concluded that Windows 2000 users should plan to begin migrations beginning in early 2008 and most Windows XP users should pursue a strategy of managed diversity, bringing in Windows Vista on new machines starting in 2008.

These recommendations have been misinterpreted in some instances and have led to several client questions. We are not saying to ignore Windows Vista until 2008 — we're saying to be ready to deploy it in 2008. To be able to deploy Windows Vista in 2008, a significant amount of work must be done to prepare. Deployments don't just happen overnight. It will take many organizations about 18 months from the time Windows Vista ships to test applications, get independent software vendors (ISVs) to support applications, build images and run pilots. Organizations that ignore Vista until 2008 will not be ready to deploy it until 2010.

The biggest issue is application compatibility. There are two issues here:

1. Will my applications run on Windows Vista?
2. Will my application vendors support their applications running on Windows Vista?

For a mission-critical application, even if the answer to No. 1 is "yes," a "no" answer to No. 2 may be enough to delay deployment. Vendor support for new client operating systems (OSs) doesn't happen overnight either. In 2003 clients told that they had just received new versions of certain vertical business applications that were finally supported by the vendor on Windows 2000, a 3-year-old, one-generation-behind OS. Similar delays will likely be common for vendors supporting their applications on Windows Vista.

Add to this the complication of organizations having hundreds or thousands of applications to test (we estimate that for organizations with 5,000 to 50,000 PCs, dividing their number of users by 10 can give a good indication of how many applications might need testing) and you can see that the timeline required for preparation is quite long.

Several clients have already reported that the most recent versions of applications from several vendors are not supported on Windows 2000. Another milestone to be aware of is the end of Microsoft extended support, which will come in mid-2010. Thus, Windows 2000 users that begin a migration to Windows Vista in 2008 will have about two years before they stop getting security fixes from Microsoft, they but will likely already be encountering support issues from other ISVs.

Organizations running Windows 2000 absolutely need to be working on Windows Vista from the time Microsoft releases the product to manufacturing (RTM) and should be talking to vendors of critical applications to discuss application support timelines before Windows Vista ships. This will allow them to start deploying in 2008 so they get their users off before ISVs drop support for their critical applications or Microsoft ends support for the old OS.

Organizations running Windows XP could wait a little longer to start deploying Windows Vista and can migrate as they buy new hardware, leaving older PCs running Windows XP in place until they are replaced (a slow roll vs. the "forklift" migrations Windows 2000 organizations need to do). The reason we suggest migration through hardware attrition is that physically touching each PC and installing a new OS is usually an expensive, manual task. And to the labor cost you need to add the cost of the Windows license upgrade. For a PC you will only own for a relatively short time, it probably does not pay to spend a few hundred dollars upgrading it. Only consider upgrading a PC that has more than half its useful life, or at least two years of useful life, left.

It will take most organizations at least 18 months of planning and testing before they can start deploying a new OS. Organizations that want to start deploying Windows Vista on new PCs in 2008 need to start working as soon as the OS ships.