Microsoft has released the first beta test version of Windows Vista, formerly known as Longhorn, and it would be a good idea for companies to try it as soon as possible. Compared with the simple transitions from Windows NT4 to 2000 to XP Pro, it may come as a bit of a shock.
Vista is still recognisably Windows, underneath the new Aero 3D interface. However, it includes some significant changes that could cause problems. These include both hardware and software compatibility, and changes to the user experience.
Hardware compatibility problems may result from changes in the Windows driver model. Vista is intended to be compatible with old XP drivers, but there may be problems with some devices.
Software compatibility problems may result from Microsoft's attempt to make the system more secure by using the sort of limited user mode familiar from Unix and Linux systems.
Many Windows security problems result from users and applications running with root (administrator) privileges. This was not supposed to happen, but followed from Windows NT inheriting applications from the Dos-based version, where there were no such restrictions. It proved difficult to restrict these privileges later, and most companies chose compatibility over security.
With Vista's User Account Protection, Microsoft wants everything to run with limited privileges, even if the user is logged in as an administrator. Users will then have to enter a password to authorise actions that could compromise the system. Given the way many Windows applications have been written, this may be too often.
From the usability point of view, the biggest challenge in Vista may be the introduction of virtual folders, which follow on from the virtual folders in Outlook XP. Virtual folders are not real folders. Instead of files, they contain links to files that are in other real folders.
Virtual folders are very useful because they let you create folders based on searching your hard drive for files or types of files or for metadata. One virtual folder could, for example, hold all your photos, while another could hold all the work for a major project - and one photo can be in both folders simultaneously. Except it isn't really; it is in a real directory somewhere else.
It remains to be seen how ordinary users will cope with this. Unless the real and virtual folders are clearly separated (which sort of defeats the point) I can see confusion arising when they try to move real files into virtual folders, or delete virtual items thinking they have deleted the real thing.
There is more than a year to go to Vista's launch, and it is too soon to say how well it will work. I suspect it will polarise the market into lovers and haters, but the people with most to worry about are the "don't knows".
Jack Schofield is computer editor at The Guardian