It’s hard to picture the Windows Taskbar’s evolutionary past at Microsoft, because… well it was developed in the dark. A couple of months ago, I sat down with Chris Holmes and dug up builds from each development milestone at Microsoft and activated the new, secret Taskbar for comparison.
Figure of Milestone 1, 2, and Beta (Milestone 3-like) Taskbars displayed vertically, respectively.
The Milestone 1 Taskbar was switched on with the addition of a Boolean DWORD value named EnableCHS, placed in the HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced key. One could infer CHS is a symbolic reference to the Chinese and their government’s way of shrouding everything in secrecy. Microsoft has come out and said CHS stood for Can Has Superbar, a reference to “lolspeak”. This iteration of the Taskbar featured very basic grouping features, live preview, and early support for “pinning” although not completely functional.
Milestone 2 builds featured an improved Taskbar, primarily focused on improving past pinning and grouping work. It also featured the beginnings of what we now know as Jumplists and Aero Peek. Unlike the previous Taskbar, the Shell performed more vigorous checks on who you were, under the Microsoft corporate umbrella, to determine if you were authorized to use the new Taskbar. One could infer these additions denote the point in time in which “new Taskbar builds” of Windows 7 had to be shared outside the Shell group for further work (e.g. the teams that work on Libraries, Find and Organize).
At the end of what you could call the “private development” tunnel, Microsoft started work on Milestone 3 builds of Taskbar. It is at this time, pinning and grouping features were smoothed out, attention jerking elements were removed (e.g. the awful white gradient), and the more subtle icon resources installed in preparation for the upcoming technical preview. Unpictured, Jumplists still had the small arrow that appeared upon hover over a Taskbar button.
The Milestone 3 Taskbar received little polish before being pushed out to the public in the first Pre-beta build of Windows 7. While demoed at the Professional Developers Conference in 2008, the Taskbar was not intended for public use. Having received a tip of the new Taskbar’s existence, however, I circumvented its Milestone 2-based protection and developed a tool to enable its public critique. (After all, we, the users, were the ones that were going to be using this from now until the next major Taskbar change. I felt it was important to perfect it now before code freeze.)
Updated July 30, 2009: Added proper definition of CHS, as per Microsoft.
Xlinksoft 
