Microsoft has
published a set of guidelines on which decisions to make now, so that your computer will be ready to run Windows Vista. They claim that any mid-range AMD or Intel processor will do, and even low-end ones will pack enough power to run Vista. 512 MBRAM is advised, but for more advanced users, 1GB is recommended. As for graphics card:
"If you are building or buying PC today, you probably want to avoid the low end of the current GPU range and make sure you get a GPU that supports DirectX 9 and has at least 64 MB of graphics memory." My take: I can confirm that the Windows Vista December CTP, with all the effects turned on, runs more than fine on my aging AMD Athlon XP 1600+, 512MB SD-RAM, Ati Radeon 9000 128MB DDR-RAM (DirectX 8 compatible card, so
not a DX9 card). Just so you know.