The overall concept of the I/O Restrictions, when enabled, is that everything is denied unless it is explicitly
allowed (with one or two exceptions). So unless you add a directory to the 'allowed' list, unless it is the current
directory and the 'Permit Read/Write in Current Directory' option is checked, then the directory in question is not
permitted to be accessed.
The exceptions are as follows:
The installation directory of POV-Ray for Windows (as given by the registry) is permitted to be used for read
(but not write). This includes all subdirectories of the install directory (except as below). Note that you can alter
this setting if you like.
The INI subdirectory contained within the POV-Ray for Windows install directory, as given by the registry, is
permanently write-protected (unless the I/O Restriction system is turned off). Even if you grant permission to write
this dir from the below INI file, writes will not succeed. This is to prevent the INI file that contains the I/O
Restriction configuration from being modified by a script to grant itself more access next time POVWIN is run.