An SD card basically expands the size of the hard drive. You can't transfer the games to a different wii, nor can you play the games from the SD card. If you're sending your wii in for repairs then you should be fine, when you get it back it'll have the same system ID and such so you'll be able to transfer them from the SD card. You can actually just re-download them whenever you need to from the Internet channel though. Once they've been downloaded to a wii once, you can download them again for free as long as you're using the same wii.