My sense of humour I'm afraid. By the space bar I was referring to the space bar between my ears - which I actually hit violently!!!

I had overlooked that XP didn't actually require a floppy disk. Once I remembered this I 'hit' the relevant key (F12) where I was asked whether I wished to boot from the hard drive, or from the external DVD drive. Of course I chose the latter and all went swimmingly from there.