I managed to install 'Windows Vista Ultimate' Beta 2 (Build 5384) on a Dell Precision work station 360. The machine was running a 3.2 G Hz Pentium 4 and had 1GB main memory and 80GB SCSI disk. It also had a NVIDIA Quadro Fx 500 display card with 128 MB graphics memory.
Pre Windows Vista, the above configuration can be considered 'good-enough' for normal usage. But I was surprised to find that the Vista gave it an overall System Performance Rating of just 2!
With this rating, Vista will not enable the 3D desktop features. I guess, 128 MB graphics memory is too little for Vista!