Never in its history has Microsoft (MSFT ) had to wait so long between Windows releases. When Windows XP launched in October, 2001, researcher Gartner Inc. expected the software giant to gin up a new version within two years. But Microsoft's ambitious follow-up to Windows XP, code-named Longhorn, has bogged down in delays. The company rarely discloses timelines for products, lest it miss its targets. But in copies of two e-mail messages obtained by BusinessWeek, Microsoft lays out a roadmap that shows Longhorn debuting in the first six months of 2006.

What's more, the e-mails disclose Microsoft's plans to cut some of the most far-reaching pieces of Longhorn in order to get the product shipped. For instance, Microsoft had planned to overhaul the file system, the way information is stored. The goal had been to change the way files relate to one another, so that users could quickly find documents, e-mail, and photos that have some connection to one another. It would be easy, for example, to locate not just digital photos, but e-mail from people in them. It's an enormous undertaking.