Windows Vista Capable

Modern processor (at least 800 MHz)1
RAM 512 MB
DirectX® 9 capable
(Windows Display Driver Model (WDDM) support recommended)

Windows Vista Premium Ready

1 GHz 32-bit (x86) or 64-bit (x64)1
RAM 1 GB
GPU Runs Windows Aero2
Graphics Memory 128 MB
HDD 40 GB
HDD Free Space 15 GB
DVD-ROM drive3
Audio output capability
Internet access capability

Windows Aero requires the following:

* DirectX 9-class graphics processor that supports the following:
* WDDM
* Pixel Shader 2.0 in hardware
* 32 bits per pixel
* Adequate graphics memory
* 64 MB of graphics memory to support a single monitor less than 1,310,720 pixels
* 128 MB of graphics memory to support a single monitor at resolutions from 1,310,720 to 2,304,000 pixels
* 256 MB of graphics memory to support a single monitor at resolutions higher than 2,304,000 pixels
* Meets graphics memory bandwidth requirements, as assessed by Windows Vista Upgrade Advisor running on Windows XP

Details:

http://www.microsoft.com/presspass/press/2006/may06/05-18GetReadyPR.mspx