The final version--formerly known as--is due to be released early next year following a long and protracted development.
Thewas recently made available, with 100,000 downloads made since the end of April. But analysts are predicting , will be key.
According to Microsoft, Windows Server 2008 will initially include a beta version of its virtualization application, which will be updated when the full version becomes available within 180 days.
David Bradshaw, analyst at Ovum, emphasized the importance of virtualization. "Virtualization is the silver bullet. As with any silver bullet, you have to treat it with caution," he said.
He said this will be very valuable for chief information officers who are being put under increasing pressure to make better use of assets.
Bradshaw said leading-edge companies and those due for a server operating-system upgrade are more likely to go for Windows 2008. But, he added, much will depend on issues such as the extent to which users can mix and match server operating systems. "Companies will probably move very slowly," he said.
And Roy Illsley, senior research analyst at Butler Group, said: "I think it will become the default server operating system. It will over time become significant, but where it's going to be challenged is virtualization."
Illsley added: "Without it (virtualization) people are going to be looking at it and wondering 'what's the benefit?' Virtualization is the one that's key."
Butis already getting crowded, and Illsley envisages a "bit of a battle" ahead.
He predicts a "fair proportion" of companies will buy Longhorn on its release but are more likely to use it for testing, with only 10 percent potentially taking it into production.
According to Illsley, companies may also be cautious about moving to the new operating system and are more likely to wait for the first service pack to become available.
But he said that Microsoft has a pretty strong base to work on with a significant presence in the server operating-system market.
As well as virtualization, Microsoft touts other innovations in Longhorn, such as improved control and security features.
Microsoft UK Windows server product manager Gareth Hall said that customer reaction suggests "there's a fairly serious interest in the product".
"Anecdotally, it's been pretty positive. People are pretty eager to get hold of this. We're encouraged and optimistic," Hall said.Tim Ferguson of Silicon.com reported from London.