To uninstall Unlaunch simply boot the "UNLAUNCH.DSI" file (
download here, if you've got 1.8+ you can boot holding A + B and it should be "Unlaunch DSi Installer" or "UNLAUNCH.DSI" in the list, if you've got 1.7 or lower rename it to "bootcode.dsi" and put it in SD root) and choose "Uninstall" from the menu, you can then delete anything you don't want from your SD. The "private" folder is system stuff and "DCIM" is SD photos, other than that everything else is probably fine to delete.