http://www.microsoft.com/windowsvista/getready/capable.mspx
What is a Windows Vista Capable PC?
A Windows Vista Capable PC includes at least:
* A modern processor (at least 800MHz1).
* 512 MB of system memory.
* A graphics processor that is DirectX 9 capable.
What is a Windows Vista Premium Ready PC?
A Windows Vista Premium Ready PC includes at least:
* 1 GHz 32-bit (x86) or 64-bit (x64) processor1.
* 1 GB of system memory.
* A graphics processor that runs Windows Aero2.
* 128 MB of graphics memory.
* 40 GB of hard drive capacity with 15 GB free space.
* DVD-ROM Drive.
* Audio output capability.
* Internet access capability.
What is a Windows Vista Capable PC?
A Windows Vista Capable PC includes at least:
* A modern processor (at least 800MHz1).
* 512 MB of system memory.
* A graphics processor that is DirectX 9 capable.
What is a Windows Vista Premium Ready PC?
A Windows Vista Premium Ready PC includes at least:
* 1 GHz 32-bit (x86) or 64-bit (x64) processor1.
* 1 GB of system memory.
* A graphics processor that runs Windows Aero2.
* 128 MB of graphics memory.
* 40 GB of hard drive capacity with 15 GB free space.
* DVD-ROM Drive.
* Audio output capability.
* Internet access capability.