fail install hang windows 2006 microsoft corporation

Booting off the Beta2 dvd downloaded yesterday, Vista is loading files - gets to the end of this first screen. It then goes black and then you get the "swish" with Windows 2006 Microsoft Corporation The swish goes once across the screen and as it starts to go across the second time the whole pc hangs. Numlock/capslock keys don't light up, ctrl-alt-del don't do anything - I have to switch the machine off with the power button
Any ideas? I don't want to run from my windows partition as that it where i want to install to (as a new installation, removing the existing c: partition)