Hello,
I have just found on http://www.faitmain.com/fs2002
a wonderfull little program made by Gerard Durand and called "Find All Duplicate".
It is designed to eliminate duplicate texture files in Fs 2002 between each installed scenery and the main texture directory.
Scanning sceneries between them is offered as an option.
Very easy to install and to use,all instructions provided.
Only restrictions:
a) it scans the ADD ONS directoru only (so far)
b)it is a very small program (17 k) downloading with acceleration systems may fail.
I have used it yesterday and found 5043 duplicate files.
Quite a lot of space to save on HD.