From Microsoft's point of view, PCs will be "Vista-capable" or "Vista Premium Ready". "Vista-capable" computers will be able to run Windows Vista and use it minimally. "Premium Ready" PCs will take advantage of Vista’s Aero graphic engine.
To be Vista-capable, a machine needs at least an 800MHz processor, 512MB of memory and a graphics card that can run DirectX 9. To carry the Premium Ready designation, a PC must have a 1GHz processor, 1GB of RAM, and a graphics card that supports Vista's graphics-driver model.
Today Microsoft will talk about these two labels and how will they be used by retailers to characterize their systems.
More about the system memory and graphics memory necessary for Windows Vista at eweek.com.
To test if your Windows XP is ready for Vista, you can download Vista Upgrade Advisor.
Windows Vista launch delayed once again
Who can market Windows Vista (or why would you buy Windows Vista)?