The program you need, to transfer MP3 files to an SD Card is called 'SD Jukebox' and it was included in the 'Audio PC Writing Kit SD-CB7', together with a suitable SD Card Reader/Writer module. As far as I am aware, the kit is no longer available from Panasonic, however, the kit does occasionally appear on eBay. Another possible source is Walt Tenay in USA : http://www.wtenaykeyboardstudios.com/main.html
Midi files can be saved to an SD Card but NOT just by copying from a folder on your PC to a card. You don't need any special software to do this and if you care to email me, I'll send you the procedure. My email address is in my profile.
[This message has been edited by Bill Norrie (edited 07-27-2010).]