Thanks for the replies Chad and Andy. I keep a disconnected emergency HD in my PC case which allows me to run XP and internet etc., Using this, I renamed the $windows ... directories on my normal HD. On reboot, I got an install error message then was presented with a boot menu with the options Windows XP and Windows Vista Install. Think this was a result of having EasyBCD installed (providence). Anyhow, selected Windows XP and now everything is fine. Deleted the Windows Install option using EasyBCD front-end.
Still have the Vista install issue but suspect there is a driver
or some piece of hardware on my system that the OS is not happy with. Will investigate later.