A. Desktop composition is the technology used by Windows Vista and Windows 7 to provide the advanced Aero features such as translucent borders, live taskbar thumbnails, and Flip 3D. These features are all facilitated by each application drawing to its own off-screen display. The Desktop Windows Manager (DWM) uses composition to layer the application-specific off-screen displays together on the user's main desktop. Because the DWM knows each application's window content, it can use that content for more than just drawing on the main display, for things such as live taskbar thumbnails and Flip 3D.
To access desktop composition, the OS needs to be able to access advanced graphics functions such as DirectX components, that aren't normally available in virtualization platforms.
Several virtualization platforms now support desktop composition, including VMware Workstation 7, VMware Player, Windows Virtual PC, and Parallels Workstation 5 for Mac. Guest OSs in virtual machines on these platforms can access Aero themes and perform all the desktop composition related features.
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