Thank you, Mike for your very prompt reply.
I'm delighted to learn that I apparently can simply do a clean install with my 64 bit disc; I had thought that as my 32 bit installation had been activated that I couldn't reuse the code number to re-install using the 64 bit one.
I am 85 years old and have plenty of spare time to do the re-installation so there should not be any problem.
Thanks once again,
Regards,
paddyjoe.