Back in 2007 the Windows team started working on the look of Windows 7.
Usually Microsoft doesn't show any of the designs it tried out along the way, but the Windows desktop team revealed several of their early designs and what they learned from them as an example at the recent MIX user experience conference.
The first attempt, in early 2006, was a taskbar with thumbnails of open windows instead of icons. The problem with that, he points out is that "they become small and most of time they turn into white squares that don't help much".
Here is an example :
Bat Signal and Aladdin
The next prototype, in February 2007, was called the Bat Signal; when you moved your mouse over an icon in the taskbar, the full window would pop up on screen, highlighted by beams of light (a little like the Batman signal projected over Gotham City).
Bat Signal made it easy to find the right window but it caused other problems: "sometimes people toss the mouse down to the bottom of the screen when they're typing because they don't care where the mouse is and the Bat Signal pops up and that's really intrusive in their flow."
Bat Signal evolved into Aero Peek in Windows 7; you can hover over an icon to get thumbnails and hover over a thumbnail to get a preview of the window.
Full read at
TechRadar.