Hi MEX,
S1fwx is used to extract the firmware of your player. This is useful for backup purposes and if you want to reskin your player and use your own images instead.
The s1res tool is view the firmware extracted using the s1fwx tool. You can also use the s1res to modify the text and images in the firmware then upload it back to your player.
Instructions are here:
How to: extract firmware of your player using the S1fwx tool
How to: Modify your firmware using s1res tool