So, say I share my system (C) drive through windows (E.g. properties -> Sharing -> Advanced Sharing -> Share this Folder). I can then access this drive at \\Comp\C on another networked computer - all is well.

However, if I insert a removable (USB) disk, say "E", and proceed to share it the same way, when I attempt to access \\Comp\E (either directly or through browsing) I get an error:

Windows cannot access \\Comp\E

You do not have permission to access \\Comp\E. Contact your network administrator to request access.

Now, the permissions (Advanced Sharing -> Permissions) are set with "Everyone" having read access (same as the internal drive), so this doesn't make a lot of sense.

Also of note, I have an SSH server on my computer (through Cygwin) and even through SSH (logging in as an administrator user) I cannot access /cygdrive/e (although /cygdrive/c is accessible).

As a final note, the drive is of course accessible on the host machine (E:\), and also at \\Comp\E on the host machine.