make clean (really!)

Hello,


i try to build the newest snapshot while still having an old one on the 
disk.

Unfortunately, 'make setup' crashes when looking for Cross Tools.

Anyway, i don't think it has something to do with the new snapshot, but 
some hidden setup files storing my old config.
Because, when i rename my old snapshot and then try to rebuild it, it 
crashes as well.

So, how do i make the setup really clean?
'make clean' seems not enough, since it still knows some old configs.
Where are those hidden files, and how to remove them?


Thanks.