Microsoft classifies computers capable of running Vista into two categories–you have the Vista Capable computer, which can run the OS but not with all the visual features, and then you have the Vista Premium Ready computer, which will be capable of running Vista in all its glory. A Vista Capable computer needs to have a processor running at least 800 MHz, 512 MB of RAM, and a DirectX 9 class graphics card. A Vista Premium Ready computer requires a 1 GHz processor, 1 GB of RAM, and a graphics card with at least 128 MB of memory (DX9-compatible too, as well as one with the correct WDDM drivers). Such a Premium Ready PC will take advantage of Vista’s high-end features.
Essentially, Windows Vista’s Basic interface will work with virtually any graphics hardware that supports Windows XP or 2000. Also offered is the Windows Vista Classic look, which essentially offers the same UI as Windows 2000 does. While a PCI-Express video card is not a requirement for Windows Aero, Microsoft recommends one over an AGP device due to the greater bandwidth of the interface.