Thank you very much to the person who answered my last question on 
booting netbsd and helped me ... erase my whole disk: no problem I get 
used to it and the error was mine. Anyway, the installation process runs 
much farther now but sysinstall stops at the drive selection: after 
having chosen "re-install sets or install additional sets", when I 
select my wd0, the answer is :

"It appears that wd0g is not a BSD file system or the fsck was not 
successful. The upgrade has been aborted."

I had however made my partitions very conscientiously and wd0g IS my 
A/UX usr partition.

Apart from that I also have a doubt about the sets: I have a little scsi 
hard disk that I have partitioned in HFS+ and A/UX free, to make it 
available for the netBSD sets. How could I copy these onto the right 
partition (I suppose the sysinstall will not see them on the HFS+ 
partition, will it?).


Thank you again (and sorry for this durable demonstration of ignorance) !