hey there's another post slightly related to this, regarding card readers, check it out as well. anyway card readers aside, let me elaborate. i the micro sd i bought for my r4 was a lovely 2GB Kingston. i loaded on 3 roms (untrimmed), and they played fine. later that day i loaded on the trimmed roms plus another trimmed rom (having used the rom trimmer included on the DS cd) and removed the old ones. i threw some mp3s on too, about 15. having read about hot card readers, i kept check of mine. it got a little warm. anyway the ds played for a while, then froze. the card was DEAD ! luckily it should be replaced , but for future reference, what do we know about micro SDs that can prevent ours from dying? i asked one tecchie about them and he reckoned MP3s are no good, that they burn out your card and drastically reduce its lifespan. any info on micro sds would be great.