Sources close to Microsoft told me this week that the software giant has started a mysterious new software project called Project M, which might be a replacement for the Windows shell in Longhorn. Heading Project M is none other than Hillel Cooperman, the user experience guru who presented Longhorn's UI ideas to developers at the Microsoft Professional Developers Conference (PDC) in October 2003. Cooperman reports directly to Chris Jones, who recently returned to the Windows client team. Jones, in turn, reports directly to Will Poole, senior vice president of Windows Client Business. Project M is described internally only as Windows "shell enhancements," a mysteriously vague description. The project is secret even to most people at Microsoft and won't likely be added to Longhorn until the beta 2 or even the Release Candidate 0 (RC0) release. One source theorized that Project M is to Longhorn as Luna was to Windows XP: Early XP (then known as Whistler) betas used a UI called Watercolor that Microsoft eventually dropped. The UI in today's Longhorn builds, which we'll soon see in beta 1, could likewise be pushed aside for something more visually impressive