FS Toolbox is a dangerous program, and it is advised that you only use it if you have a sufficient understanding of how the Wii system memory works and what files not to mess with. You should probably use BootMii to backup your Wii before continuing. FS Toolbox is a NAND browser that can dump files from the nand to sd card and write files from sd card to the nand,with this you can edit files on the nand to test stuff out and to have backups of your files if something ever goes wrong.

The creator of this application takes no responsibility for the damage that you may cause to your console when using this.

http://wiibrew.org/wiki/FSToolbox