The Register took a look at the hardware requirements needed to run Windows Vista Premium in its full glory:
A Windows Vista Capable PC does indeed require "a graphics processor that is DirectX 9 capable", while a Windows Vista Premium Ready PC has more stringent specifications. The difference between Vista Basic and Vista Premium is the Aero user interface, which adds glass-like effects to the appearance of the GUI.
A Vista Premium Ready PC requires a DirectX 9 GPU that supports a WDDM Driver, supports Pixel Shader 2.0 in hardware and defines colours using at least 32-bits per pixel. These are the important features and, in addition, the GPU also requires adequate graphics memory which Microsoft defines as..