Corrupt / Unreadable Graphics setup on Installation

I am installing the latest version of Windows Vista, doing an upgrade from my
XP SP2 system. The install process runs through the Copying files, Gathering
files etc... fine. After Gathering all the files it needs (100%) the setup
requests to restart, it then boots to an unfamiliar boot loader (white scroll
bar with 2006 copyright).

From here it seems to load what can only be described as a dot matrix
display, where each dot takes up around 20 pixels on my screen ala:

.. . . .
.. . . .
.. . . .
.. . . .

Essentially the whole screen is black, apart from the edges of my mouse
which has these dots, that are coloured in several diffrent bright colours.
The mouse wraps from left to right 5x (aka if I move the mouse to the right
of the screen it appears to the left, and it is able to do this 5 times
before reaching the end. ) The vertical doesnt wrap around but from moving
the mouse around it is obvious that there is more being rendered off screen
that I cannot see.

This has happened 3 times in all now, the first two times I also got some
vista-esque window from what i could tell, and when I did a hard reset again
(as it was all I could do) it booted back in to XP saying that I the
installation had failed.

Now on my third installation it seems to have locked in to this state, but
without any windows and I just get the highlighted edges of my cursor. When
ever I reset it boots back to this dot matrix like display and I am unable to
do anything useful. I dont think windows vista has installed completly, I
think this is booting in to the vista install system.

I am assuming this is something to do with corrupt display adapter drivers
or similar, yet my graphics adapter does seem to be valid (in the ATI 9600
range.)

I have searched around and not found anyone else with this problem. Ideally
I would like to boot in to windows vista properly, failing that I would hope
to boot back to XP.

Thanks in advance
-Matthew Lloyd