Now Vista has its share of problems, and seeing how 1GB is always in use by the OS is blood curdling, but it ran well enough on:
AMD Athlon 64 X2 4200+
2GB DDR400 RAM
300GB HD
Nvidia 7900 video card

Runs spectacular on
Intel Q6600
4GB DDR2-800 RAM
320GB HD
Nvidia 8800GTS video

Plus, Vista has some nice features too... though don't ask why Microsoft won't use encrypted USB dongles to store serial number/activation code when they want people to use USB flash drives that contain encrypted serial number/activation code for Bitlocker...