Well that pretty much answers myt question, especially as I have just
obtained a MS keyboard with a USB connector and didnt actually know tjhat
you could use them intercahngeably]

Now however i have a more pressing problem about which I need to get an
answer: This was one broken system.

When I turn it on, nothing happens on the screen or in the computer beyond
the power button light light and fan coming on when I press the button on
the keyboard or on the unit itself. No gong, no perceivable HDD activity
etc

Is there some sort of reset button or start sequence I can try (I am not
sure I can get as far as doing anything with the keyboard??) or is it time
to open the thing up and start looking around inside it for blown fuses on
the power supply? (If so, how or is it worthwhile or is the problem
OBVIOUSLY the whole power supply in this situation, - is this a known set of
circumstances as well)?