A Windows Vista Premium Ready PC includes at least:
1 GHz 32-bit (x86) or 64-bit (x64) processorą).
1 GB of system memory.
Support for DirectX 9 graphics with a WDDM driver, 128 MB of graphics memory (minimum)˛, Pixel Shader 2.0 and 32 bits per pixel.
40 GB of hard drive capacity with 15 GB free space.
Audio output capability.
Internet access capability.
Ultimate has the most features. Its the most expensive but its what I would get.