SD Explorer is undoubtedly the easiest to use but there are alternatives which are free.
Not sure about the SD Manager at Mister Music but it sounds similar to the SD Card Tool programs which I helped Thomas Konig develop, one version for Technics files and one for midis (SD Explorer can't handle midis). These were free at the time, but never fully finalised, nevertheless worked well enough last time I used them (a few years ago now!).
Alternatively the Keysoft SD Techmanager 7000 program which was pretty expensive at the time is now effectively free since the company was wound up, and Roland Schmidt provided a free keygenerator when he closed down so you can register and use the full complement of facilities. This has the advantage over SD Explorer in that it can handle midis on the card and edit favourites, user playlists and song medleys on the pc. http://www.keysoftservice.ch/keygenerator.htm
Using any of these programs without first backing up your card if important work is involved is naturally particularly foolish
[This message has been edited by technicsplayer (edited 11-07-2010).]