Vista Live Taskbar Thumbnail

Aero also enables dynamic window animations, so that when you minimize a window to
the taskbar, it subtly animates to show you exactly where it went. This kind of functionality
was actually first introduced in Windows 95, but it has been made more subtle and
fluid in Windows Vista. Additionally, Aero enables Live Taskbar Thumbnails: When you
mouse over buttons in the taskbar, a small thumbnail preview will pop up, letting you see
the window without having to actually activate it first, as shown below