cannot set file permissions

[Eduard Hoenkamp]

I simply do not manage to set the permissions on files on (non-boot) 
partitions under OSX 2.2.4 Before you shoot from the hip: What I 
tried in vain: (1) command line - chmod as superuser, chmod while 
logged in as superuser, and vsdbutil (2) GUI - changing via 'get 
info', and trying several utilities found on the web. (Note: I have 
two decades of Unix behind me, so I assume it is OS X and not Unix 
that does me in.)
Dazed & confused, hence grateful for your input, Eduard.