Windows Vista Pro Corporate Edition will be released in December, all home versions in January 2007. I have this from my contact at Microsoft.
Requirements for Pro version as recommended by same friend are all P4-AMD Athlon 2.0GHz +, 1GB RAM, 256Mb DirectX9.0 GPU/VPU and at least 9GB free for OS, Office and SwapFile.
I tried that BETA on my machine and its seriously full up with unoptimised and unfinalised software and services and its toll on your current specifcation is not indicative of the final optimised build.
... However upon a recent visit to Microsoft UK (1 mile from my work!) I have seen a late build of it running on a medium spec Dell Latitude notebook and it had the latest build of the following running really smoothly:
Aero (Hardware accelerated GUI)
Media player 11
Office 2007
Internet Explorer 7.0
Microsoft Virtual Server
Very amazing GUI btw, with live previews on the taskbar and in application switch mode!
