This forum is for install questions on supported players manufactured by Toshiba. There is a specific list of players in the main forum page showing which players are appropriate to ask about here. You'll note that in the list of players, the Gigabeat S is not listed for this section of the forum. This was not oversight or a mistake.
Right now there's not even an absolutely finalized install process. If you wish to know more about what is necessary to have Rockbox on the player, read the development information and see what the current installation options are.