In the beginning, there was the sidebar! Early thinking in this area consisted of everything from the Microsoft Research team (via an application called Sideshow) to the MSN and Windows team collaborating on visual mock-ups, like the one pictured above. The sidebar was going to be a centerpiece in Windows Longhorn, giving you instant access to the information you most wanted to see -- everything from contacts, to news, to documents and more.

Although a the sidebar made it into Windows Vista, it was more of an afterthought by then, existing as a separate application that was ultimately unutilized and quickly abandoned.

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In 2001, flash mock-ups were created to showcase what a finalized Windows Longhorn might look like. Many different UIs were created, but only one was chosen to be the model designers and developers would code into Windows development. This particular demo spawned the Plex (the name of the theme used in M3-M4 builds) era of Longhorn development at Microsoft. Subsequent themes used were Slate, Jade, and various forms of Aero.

As you can see in this screen shot, there were massive changes planned for the Windows shell.

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Here's another conceptual shot of a Plex-themed Windows Longhorn, circa 2001.

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This is a Plex concept that extends even farther back in time than the previous two screen shots, thus showing the humble beginnings of a wild new look for Windows.

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This screen shot represents early thinking for the carousel view: a view that would allow users to view the contents of a folder in a flashy, new way. Presumably, pressing the left and right keys on the keyboard would make items spin left or right, accordingly. This feature didn't make it very far, but it was implemented and working to some extent in early builds of Longhorn!

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During the early stages of Longhorn UI ideation, countless mock-ups were dreamed up, mocked-up, then sifted through to land on the right candidate(s) for designers and developers to pursue. Here's an example of an extremely wild Longhorn UI concept that never saw the light of day much beyond what you see here.

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Every aspect of Windows was being addressed and given a massive facelift, as well as a functionality lift. This is one of countless login screens that were mocked-up by designers working on Longhorn.

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During PDC 2003, Hillel Cooperman (Tjeerd Hoek's partner in crime on the MSX team) gave an unbelievably exciting, no-pictures-allowed (though some folks, like Paul Thurrott, were given permission to take and share some pictures at the time) demonstration of Windows Longhorn that was MUCH more ambitious and FAR more visually-exciting than the Plex-themed Longhorn.

Though you can't tell from this screen shot, the background, called Aurora, animated and was to be realized via a then-new markup language called XAML. For the first time, Microsoft was going to make it easy for developers and designers to work together seamlessly -- or so, that was the goal.

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Once logging in from the previous screen, the user was sent to this absolutely gorgeous desktop. To note, this presentation was only a mock-up made and demonstrated in Macromedia Director (flash-based, basically). This look would directly inform visual development of Longhorn straight up through its cancellation with build 4094.

Though the Aero name and some of its properties (like transluscency) would carry on through the completion of Windows Vista, the lack of many of the shell changes that would have truly shown it off made it nothing like its earliest incarnation, as showcased throughout the next handful of screen shots.

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The Start menu in this Longhorn concept was animated in numerous ways: the Windows flag waves, there's an aurora animation running on the left-hand pane, and as you hovered over menu items, their respective icons would swing into view at the top of the left-hand pane. It was an awesome, awe-inspiring vision of the Start menu!

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Big glass borders gave an exciting look and feel to the shell, also providing a space for recent thumbnails. The thumbnails feature seemed odd and out of place, but at this point in time, the focus was on showing off the potential of a sleek, clean, and glassy UI that Windows users would hopefully drool over (and we did).

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The orb you see was an animated WMP gadget that gave the appearance of existing in a 3-dimensional desktop space. (In a later screen shot, you will see a much more drastic extent to which Microsoft was thinking in terms of 3D space on the desktop.) Also, attendees were given a glimpse of more functionality that one could utilize the sidebar for. Once again, the "wow" effect was achieved.

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Welcome to Phodeo. Firstly, you will notice the lack of translucency in the shell. The thought here was to keep your attention focused on what you wanted to see inside of a maximized window. If you viewed this window in a non-maximized state, Aero's translucency would kick in.

That said, Phodeo was to be a completely new experience for browsing, sorting, and working with photos in Windows. The background was an animated aurora and you could change the views of images. As shown above, images were sorted by month, and as you moved through months, the animation was kind of like a carousel, except with the smallest ends moving off into infinity and/or moving into view, depending on which way you scrolled.

Make no mistake, it was visually stunning.

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For document management, Microsoft was going with something called "stacks." It was a nifty way for displaying, organizing, and sifting through documents. Also showcased in this image is a different look and feel for the glass borders of Aero -- something that quite frequently changed, albeit subtly, in multiple early builds of Longhorn.

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Even when going out, Longhorn wasn't going to leave anything without style! Shutting down your system showcased a beautiful, full-screen aurora animation.

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Longhorn wasn't going to be all flash and little substance, no. Microsoft worked hard to showcase how Longhorn would be both beautiful and functional for everyone from average home users to demanding professionals. With strong shell integration planned, apps would be made to run seamlessly between all components of the shell: the sidebar, windows, the taskbar, etc.

The next handful of images showcase ideas for a more professional Longhorn, without sacrificing performance or beauty (theoretically, of course).

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Here's an example of Excel running within a Longhorn environment. Notice the email notification and tile in the sidebar, quickly giving users access to the most recent emails.

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Here's an example showcasing Microsoft's preview pane, where just about any type of information could be shown about a document, application, or anything else that could take advantage. Developers were going to be given access to APIs that would allow them to code whatever they wanted from their application into the preview pane.

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This screen shot shows a lot going on: document stacks, preview pane information, contacts in the sidebar, and more. Longhorn was going to make the most of providing as much information as it could, all in the most attractive way possible.

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Though you can't tell, the seemingly static image in the preview pane was actually an animation! In fact, the preview pane could consist of all moving parts, if a developer wanted to do as such for their application. In some of the later pre-cancellation builds of Longhorn, Microsoft included preview pane auroras, which all varied in color (depending on the type of folder that was opened) and were coded in XAML.

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Rounding off the "Longhorn for business" screen shots, this is an example of multiple non-maximized windows, demonstrating what I noted earlier about Aero's translucent and non-translucent states. Needless to say, at this point, Windows Longhorn was shaping up to be quite easy on the eyes while one worked!

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Just about every Microsoft service that Longhorn touched was going to be given the Longhorn UI treatment, including Live services. The screen shot above demonstrates that reach and showcases how it could, in theory, work to create a seamless Longhorn experience.

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The advent of Windows Flip was a Longhorn-based implementation of Alt+Tab. Not only were you shown thumbnails while you tabbed through your selections, but all the selections would show in larger windows in the background, thus allowing you to see even more clearly what you were selecting through.

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Windows Flip was a 2D visual effect, but with the most demanding version of the Aero theme enabled, one could enjoy Windows Flip 3D: a feature that still exists in Windows to this day. Instead of Alt+Tab, pressing the Win key + Tab makes all running tasks fold back into 3D stacks you can scroll through. It's primarily a flashy effect, but when it was first mocked-up, it was a nice change of pace that fit well with the Longhorn vision.

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For years prior to Longhorn, Microsoft had messed with the idea of 3D space on the desktop. In the small desktop screen shot in the lower right-hand corner of the image above, you can see what was perhaps the most drastic conceptualization of a 3D Longhorn desktop. In it, the wallpaper and sidebar fold back out of view, much like a door opening away from you, to reveal a sort of 3D space that housed a few ideas, including revealing another desktop or simply showing more information on the current desktop.

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In this screen shot, taken from an Amazon demo at PDC 2003, Jim Allchin showed off a rather flashy Amazon browsing experience, which utilized the preview pane and one of many 3D views. (To note, this demo was meant to also show off some of the underlying services that were being baked into Longhorn.) The theme you see here is Slate, which was rather hideous compared to the beautiful Aero theme showcased earlier. It was merely temporary.

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Here's an image that showcased Phodeo's 3D view from a different perspective.

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Yet one more of the myriad of Longhorn mock-ups created, this one showcases thinking for a sidebar/taskbar combination. Personally, I wasn't a fan of it, but the window that's open, however, shows yet another take on how beautiful the preview pane could be made to look and function. (Thanks to Long Zheng for initially sharing this image on his blog.)

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If you've fallen in love with Longhorn, then welcome to the club! Most of us who lived through its development will forever be infatuated with what was never meant to be. To be clear, it's not Longhorn that I hope Microsoft brings back with the departure of Steven Sinofsky; it's the passion and ridiculous excitement that made Windows users and developers want to tell Microsoft to shut up and take their money already.

And with that, thus concludes this little journey into Windows Longhorn: an OS that, to this day, evokes exponentially more excitment within me than Windows 8 ever has at any point through its development. I hope Microsoft can once again focus on something more than a lackluster UI.

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