Coexisting with Earlier Versions of Windows

Coexistence is an issue that affects roaming user profiles only. If you're not using roaming user profiles on your network, coexistence isn't an issue because you won't be deploying user profiles to different versions of Windows. In general, though, roaming user profiles are compatible between Windows 2000, Windows XP, and Windows Server 2003. Here are a few precautions that you can take to minimize problems:

Try to ensure that users with roaming user profiles are logging on to the same version of Windows on each computer. That means you should choose your rollout units so that you're picking up all the computers that users can access.
At the very least, make sure the same application versions are on each computer and that you've installed applications to the same path on each computer.
If you're using roaming user profiles with Windows 2000, Windows XP, and Windows Server 2003, make sure that your %SystemDrive% and %SystemRoot% are the same. Also, make sure that profiles are stored in the same path. If you're using roaming user profiles with Windows NT 4.0 and Windows XP, you should move the location of user profiles that Windows XP uses by setting the ProfilesDir property in the [GuiUnattended] section of your answer file.

There's nothing in the documentation that says user profiles don't roam between Windows NT and Windows XP. However, I suspect that this scenario isn't workable. First, Windows XP converts Windows NT–based profiles. Second, having knowledge of both versions of the registry, I suspect that subtle differences between the two are likely to cause configuration problems in the long run. If anybody suggests that you can use roaming user profiles with any combination other than Windows 2000, Windows XP, and Windows Server 2003, ask for more information and test these scenarios carefully in a lab.