A Nintendo DS R4 card is a cartridge designed to hold a MicroSD flash memory card. The cartridge is shaped like a traditional DS game cartridge, and contains software that allows your Nintendo DS game system to view and launch the programs stored on the card. Although the device has the reputation of being used to download pirated copies of games, it is not illegal to own and use for legitimate purposes. There is a thriving community of “home brew” programmers who create their own software and games for the Nintendo DS; you can legally download these games onto your R4 card and play them in your DS.
Turn the R4 card over so that you are looking at it from the back, unlabeled side. Press gently on the MicroSD card until it pops out of the R4 card. Grasp the MicroSD card gently between your fingers and remove it from the R4 card.
Insert the MicroSD card into the MicroSD card adaptor. This usually comes bundled with the card when it is purchased. MicroSD cards are only about the size of your thumbnail, so an adaptor is necessary to be able to view the card's contents on your computer.
Place the MicroSD card adaptor in your SD card reader. If you are using an external SD card reader, you will need to plug it into a USB port on your computer.
Open the directory on your computer that contains the games you want to download onto the card. Highlight the game file, which will have a file extension of ".nds," and press "CTRL" and "A" to copy it.
Click "Start" and select "My Computer." Double-click on the drive letter that represents the MicroSD card. Press "CTRL" and "V" to copy the game onto the MicroDS card. Repeat until you have downloaded all of your games onto the card.
Remove the card adaptor from the card reader. Extract the MicroSD card from the adaptor and place it back in the slot in the top of the R4 card. You can now place the R4 card into the cartridge slot in your Nintendo DS and play the games you downloaded, if you like.
There are many sites on the Internet offering free downloads of fan-created, or "home brew," Nintendo DS games. See the Resources section for several sites offering free, legal game downloads.
It is illegal to download copyrighted games for use with your R4 card.