By default, if a post is set to visibility: Private, or Password Protected, the word “Private:” or “Protected:” is prepended to the title. With a simple google search I found a code snippet that worked in replacing those words with nothing, or if I so choose, anything I like. I’ll elaborate later, but for now, here’s the plugin:
Just download the zip, and upload slim_title.php to the wp-content/plugins/ folder of your WordPress installation, then activate it in the Plugins menu.
As I said before, all it does is replace Private: or Protected: with nothing by default. There are no administrative options to this plugin, you can modify it if you are comfortable with the code.