This is taken directly from Wikipedia Requirements for Vista Updated

Graphics hardware requirements

Vista's graphics requirements are defined in relation to the different desktop experiences.
Aero Glass
Aero Glass is built on the new Desktop Compositing Engine, adding support for 3D graphics, translucency, animation and other visual effects.
Intended for mainstream and high-end graphics cards.
64 MB of graphics memory recommended for 1024x768, 128 MB for 1600x1200+.
At least 32 bits per pixel.
3D hardware acceleration with capabilities equal to DirectX 9.0c.
A memory bandwidth of 2 GB/s, and as much 8 GB/s can be supported.
Capable of drawing ~1.5 M triangles / second, one window being ~150 triangles.
A graphics card that uses AGP 8X or PCI Express x16 bus.
Windows Vista Display Driver Model (WVDDM) Drivers.
It is likely that such a configuration will be an average configuration by Vista's release in 2006. During Vista's early alpha testing stages, the ATI Radeon 9800 Pro and the nVidia GeForce FX 5900 were the only cards compatible with Aero Glass. Since then, support has been extended to most DirectX 9 Graphics cards. At this point, the nVidia FX family and up, and ATI Radeon 9500 and up are supported.
It is possible to disable the Glass translucency effects to improve performance with slower graphics cards.
Aero Glass will not be available in the Starter and Home Basic editions of Vista.
Windows Classic


Windows Vista December CTP 5270 in "Windows Classic" mode
The most basic user interface offered by Vista, which is very similar to the appearance of Windows 2000, and Windows XP with its "Luna" visual style deactivated.
Does not use the new Desktop Compositing Engine; Flip 3D, live window previews, and tearing-free window dragging are therefore not supported.
Requires Windows XP Display Driver Model (XPDM) or WVDDM drivers.
Graphics card requirements are the same as Windows 2000.
An option for corporate deployments and upgrades.
As of build 5270, the Luna visual style does not appear to be present in Windows Vista.