Vista - Hangs at 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)