I have an old HD drive that used to have a dual boot Linux/Windows installation on it. I recently added the drive to a Linux installation that I wanted to use for experimenting with Samba. I was hoping that I could use the old Windows vfat partition as a Samba share.

But, I am finding that I cannot change the permissions on the old vfat shares so that a low level Samba client can write to the share. I've tried a variety of different mount options and switches and it makes no difference. I keep getting "Operation not permmited" messages whenever I try using chmod to allow others to write to that directory or those files where the partition is mounted.

I thought maybe that there was a permissions set under Windows that is causing the problem. But I can no longer boot to that installation, so that would not be a solution.

Does anyone have any idea what the problem here is?

You need a mix of uid/gid and maybe an umask setting for the partition, and even then it'll be writable only by that single user.
Look at "man mount" under "Mount options for fat".

vfat file systems have no file table entries for permissions, owner, etc. Linux fakes these things by applying the mount point directory characteristics to all of its subdirectories and their files.

Linux is also sticky about changing the characteristics of an active mount point. So the way that I would approach your problem would be to dismount the vfat partition so that the mount point is just an ordinary empty directory. Then set the ownership and permissions to whatever works best for every file on the vfat partition. Then remount the partition.

mount it with umask=0222 option and that should fix your problem