The product is designed to replace Windows 95, Windows 98 and Windows NT 4.0 -- older versions of Microsoft's Windows operating system that many corporations still are using, despite the fact that Microsoft no longer provides security patches for them.

A hybrid of Windows XP with Service Pack 2 and Windows XP Embedded, Eiger gets its name from a mountain in Switzerland.

Eiger reportedly runs best on a system that has a Pentium II processor , 128 MB of RAM and a 500-MB hard drive. However, it also can be used on machines with older Pentium processors and as little as 64MB of memory.

Designed for networked environments, Eiger will not run Office or other business programs on individual machines. Rather, it is designed to run server -based applications.

The Eiger system is designed to be transitional, providing companies that may not be ready to replace their older units with a more-secure option until they can make the switch to Windows XP -- or even Longhorn, Microsoft's upcoming next-generation operating system.

Microsoft group product manager Barry Goffe told reporters that the product is in the very early stages of development with no established launch date or pricing. A few dozen early customers will have the opportunity to use a preview version of the new OS this week.