I could back up from the " back up" most of the files, than tryed to format whith disk control ice but , one of the partition stayed on the finder when i start the process, the processing window don't start so i must reboot.
A little miracle happened at reboot...do you want to initialize ...yes yes yes...and the firewire disk was back on the desktop.
It seems to work untill now but i'm wondering if it's not better to reformat..?
I can maybe install osx on one partition of my internal disk to get disk utility seeing my firewire disk, i got an install of 10.2.3 is it ok for that...?
Thanks very much for all the infos, links and help...
GR