I've seen alot of topics on the internet about this problem and eventually found out the solution by myself. I wanted to use a .sav from an emulator to play a backup on my DS. The problem was that simply replacing the .sav resulted in a save corrupt message, or didn't work. This is how I fixed it: Take your emulator's .sav and rename it to match your backup .gba name. Then, make sure you can see file extensions and change the .sav to either .sa1 or .sa2 Finally, power your DS and go on the GBA game. Press select and choose the appropriate option: 1 -> Default, it replace the current save file with the .sa1 2 -> Default, to remplace it with the .sa2 I hope it will help someone and that it wasn't allready answered.