In case someone has this problem again, the solution is very simple:
*With GCMM you extract all saves and place them where you want (either in SD or hard drive).
*Then you format the MC and inject only a save, in this case I will use the Custom Robo (
http://www.gametdb.com/Wii/GXCE01) one.
*Once you have your MC with only one save, you choose the option of 'RAW Backup' and GCMM will make a copy of all your card (either in SD or hard drive x2).
*When you have the file in .raw format, you only have to rename it with the product code of the game whose save was inside the MC without the final 2 numbers. (In my case, Custom Robo, the file will be called GXCE.raw).
*After this you only have to place the .raw file in the Nintendont saves folder (either in SD or hard drive x3).
I have no idea if there is a noob guide of how to do this (even if it is so simple), if there is not, I can post it as a thread apart.
