• If you use lighttpd as webserver the .htaccess-file won't do anything. But you can use mod_rewrite and a simple rewrite-rule to achieve the same functionality:
    1. Open the lighttpd-configuration-file (/etc/lighttpd/lighttpd.conf on debian).
    2. Look for the server.modules-variable, usually at the top of the file.
    3. Make sure you have a line "mod_rewrite", uncommented. It should look similar to this:
      server.modules = (
     "mod_alias",
     "mod_accesslog",
     "mod_compress",
     "mod_rewrite",
     "mod_redirect",
     #"mod_evhost",
     # "mod_evasive"
)
    4. Add the rewrite rule:
      url.rewrite-once = ( "^/sites/default/files/private/(.*)" => "/system/files/private/$1" )

      Note: This may only work if you have clean URLs enabled (I use mod_magnet for that).

    5. Save the file and restart the web-server.