You can do this easily without RocketLauncher.
You can either place a shortcut to BigBox in the Startup folder in your start menu or you can use a program to change your systems "shell". A program like bbSetshell found here: http://bb4win.sourceforge.net/bblean/ will do fine, it's free and easy to use.
If you decide to go back to using the Windows shell, "Explorer" simply pull up the Windows Task Manager and run a new task and browse to bbSetshell and set it back to Explorer in there.