Frank, thanks for your reply - even though it was not really what I want to hear (but what I suspected).
I spoke to a memory man today from a well known company, on the record my iMac will only take 4 gig, off the record it will take 6 he reckons as do you, do you know what I should be ordering ?
Regarding file location, I am pretty bad, take loads of photo's and don't delete many. The set up is as follows
500gig HDD in the iMac
350gig external
1TB external
2TB external - used to be the Time Machine
4TB external - new Time Machine
I am hoping that the 2TB disk will last me about 4 years before it is filled up.
I have now about 230gigs of HDD space on board which according to what you say is quicker than the external drives accesss wise. I could therefore load new pictures onto the interrnal HDD, do what I need to do to them there. Once done can I move the location of the folder - will Aperture (or the iMac) track the move ? Once I have gone through the images I then save jpegs in various forms either for sellling as small files or as prints via an on-line service. I do keep back up DVD's of all the important events for safety but I don't like to delete anything off of the drives. Messy I know.
Anyway, thanks for the reply again.
Bill