Ahh thanks for putting me straight!
That is the other problem with Macs ... Not many people know enough about them when you want advise - unless you have somebody like 'AppleMacster' on a forum.
Just to confirm I have a '1.66GHz Intel Core Duo' with soon to be upgraded Ram from 512 to 1Gb
Thanks again
Andrew
(Just spotted X-Plane 8 on that site)