Still getting a white screenA: Bootloader.nds is broken
B: Launcher .app is broken
Make sure you renamed arm9.bin and arm7.bin to arm9 (patched).bin and arm7 (patched).bin before you converted.
Make sure you decrypted the launcher .app file before patching it.
FAT16What format is it? If under 4GB, I recommend you format it as FAT16 and not FAT32.