Just one day after the first public reports of viruses being written for an upcoming feature of Microsoft Corp.'s Windows operating system (see "First Windows Vista viruses unleashed"), the company said it will not include the feature in the first generally available release of Microsoft Vista, due out in the second half of 2006.

The feature, called the Monad Shell, provides a way for users to access the operating system using text-based commands rather than the traditional Windows graphical user interface. In the past, Microsoft has said that Monad will be part of Longhorn, the code name for both the next client and server versions of Windows.

In an interview Friday, Microsoft director of product management Eric Berg said Monad will not be included in the first commercial version of Windows Vista when it is released. But the product is expected to be included in Windows over the next "three to five years," he said. "Our intention is to synchronize it with both client and server operating systems."

Security experts had worried that if Monad were included in a widely used client, it might become an attractive target for hackers -- especially if the shell were enabled by default.

Whether it will be enabled by default is unclear. "There are multiple ways that we could introduce this technology to the client stream," Berg said.

The first Microsoft product to use Monad will be the next release of Microsoft's Exchange messaging server, code-named Exchange 12, which is also due in 2006, Berg said.

On the operating system side of things, Monad is then expected to be included in Windows Server Longhorn, expected in 2007, and could be available in a future Windows Vista release, said Rob Helm, director of research at Directions on Microsoft Inc. "Presumably, as time goes on, all of Microsoft's products will have Monad scripting interfaces," he said.