yeah like a dingus i forgot that fat32 has a filesize limit and i had formatted this sd card for fat32 because it was in an old (now not working) flashcart for my DS-Lite. Aaand I never reformatted it. I uh... I pretty much realised this the moment I posted that toot earlier ^^; but thank you all for the suggetions which came at the same moment I realised, so they did help me realise I had made a mistake ^^; Yes it's a genuine micro SD card tho, for definite. It was just formatted wrong