Nintendo's DS hand-held video game console allows players access to hundreds of games designed for both the DS itself and the console's predecessor, the Game Boy Advance. However there is also a thriving underground scene of amateur-designed, or "home brew," games and software. These can be accessed with the use of an SD card and media cartridge (also known as a flash card) such as NinjaPass, CycloDS Evolution or R4DS. Most of these cartridges use the MicroSD or SDHC varieties of SD card, though the exact type of card varies between cartridges.
Connect your SD, SDHC or MicroSD card to the USB port of your computer using the SD reader sold with your media cartridge.
Download Nintendo DS game files and transfer them to the root directory or "Games" folder of your SD card. Many home brew sites provide public domain Nintendo DS games for free download. Two such sites are listed in the Resources section of this article.
Eject and remove your SD card and insert it into your media cartridge. Insert the cartridge into your Nintendo DS and turn the system on.
Tap the top menu item on your DS start screen to launch your media cartridge menu. Select "Browse" or "Games" to bring up a list of available game files. Tap a file to launch the game.
Press and hold all your DS action buttons to return to your cartridge's home screen and select a new game from your SD card. On some cartridges, the "Soft Reset" option must be enabled in the "Options" menu before this command can be used.
Make sure to use the right type of SD card with your media cartridge. Most media cartridge retailers will offer a package deal in which the cartridge is sold with the appropriate SD card at a discounted rate.
It's illegal to use media cartridges to play commercially available Nintendo DS games. Only download and run games from sites that offer public domain or home brew software for download.