Thanks for your reply,
It appears the reason I could not clean install Vista as the 1st OS in a dual boot is due to my having the Vista Premium upgrade version only and with this version it will not allow me to. I cannot simply do a clean install of Vista and then XP as my secondary system. I can only use the premium upgrade to 'upgrade' XP to Vista, or so I thought.
I have since discovered a way in which I can do a 'clean' install of Vista and get rid of all XP files.
I can then do an install of XP which will be my secondary OS, if I decide to.