Folders and the system files should be on root, also if you are using moonshell or dsorganize, some other homebrews like quake/doom may require the .nds to be on the root and a folder to accompany. normal games go into the folders, any media files into folders as well. Try using the panasonic tool to format the sd, 4 gb and under to fat, anything over to fat32. the tool allows that to work on the 4gb. Try formatting and using rominator to put all the games on there so they validate as they are inserted. if all of that goes through and it all validates, it may just be that her cart is bad.