Hi, I have noticed a few people are struggling to get these things to work.
I shall be providing a brief description of how to set the card up, but will not be explaining where to get pirated materials from as this could be seen as aiding piracy if I do.
Right, first thing you want to do is to buy an R4DS card and a Micro SD card :)
From there you should go and http://www.r4ds.com/soft/english/English-1.08.rar
download this, it is the software you will need for the card (the firmware).
Once you have done this, extract it to the desktop, it will be in a folder called "English-1.08" open this and you will have 2 folders and 2 files, copy both of those to the Micro SD card.
After that, anything you want to put on the card to play will just go in the same place as those, I have not tried putting ROM's in a seperate folder, just stuck them in with all the rest.
hope this helps those who are stuck,