To enable Windows Aero, PC systems must meet the following criteria for graphics hardware, with either discrete or UMA solutions:
1.
DirectX 9 class graphics hardware that supports WDDM and Pixel Shader 2.0
2.
A minimum of 32 bits per pixel
3.
Appropriate graphics memory for specified monitor resolutions expressed as total pixels (X dimension multiplied by Y dimension):
1.
64MB of graphics memory to support a single monitor at resolution of 1,310,720 pixels (equivalent to 1280 x 1024) or less
2.
128MB of graphics memory to support a single monitor at resolutions higher than 1,310,720 pixels and less than or equal to 2,304,000 pixels (equivalent to 1920 x 1200)
3.
256MB of graphics memory to support a single monitor at resolutions higher than 2,304,000 pixels
4.
Graphics memory bandwidth, as assessed by Windows Vista’s built in system assessment tool WinSAT.EXE, of at least 1,800MB/s at following resolution:
1.
Desktop PC: at a monitor resolution of 1,310,720 pixels (equivalent to 1280 x 1024)
2.
Mobile PC: at the native resolution of built-in display

http://www.microsoft.com/technet/win.../vistarpc.mspx