No UI on Vista home Premium 64 bit Startup

I've recently built a PC with Vista Home Premium 64bit, its worked fine but I
think I have managed to corrupt the keyboard and graphics drivers by turning
off the PC incorrectly!

Now when the system starts up you see the bios load and it confirms the
config then the moving bar comes up showing that Vista is loading, then the
screen goes blank. I know the OS is loading fine because it logs into MSN
Messenger but there is no display and the keyboard and mouse don't respond
beyond the bios.

The keyboard and display work fine in the bios, its only when Vista loads
that they stop working!

I've tried using different keyboards an displays (which still work with my
XP box) and it makes no difference.

Does anyone know how I can fix the problem?

Try booting into safe mode. You need to press F8 repeatedly just before the progress bar screen to get the boot menu. If things work in safe mode, try uninstalling the display adapter and the keyboard and rebooting.