Fileattributes and Fat32
in fat(16/32) there is no concept of user/group/world permissions.
The only fileattibutes it knows are rw/ro and the archive bit (maybe a few more, but you might not want to know everything)
Anyway, chowning files to let other users read or write to certain files on a fat partions cannot be done.
You can however set the permissions on mount time, but remeber these affact the complete mounted partition.
(linux will not store this info on the fat partition, but fakes the permision transparently for the user,
so the permissions look like from a "real" filesystem)
Look into man mount for details, you are interseeted in "uid, gid, umask, fmask, dmask"
set them correctly and the groups you like can read /write the files.
Rember that ntfs has owner / group capabilities, and even ACL's,
but the ntfs implementeation under linux is not ready for primetime yet,
see other posts here about reading writeing to ntfs parttions.