The Nintendo DS can also play videos on its console similar to the PSP. You need to have a flash cart like R4, DSTT or M3 card. It made use of the video format DPG to play on the nintendo ds. To playback and to encode to DPG you need to Download Moonshell plus the Moon Shell Windows Tools.
Most of users should have the moonshell as it comes with your flash card. You just need the Moon Shell Windows Tools now to convert your videos.
MoonShell Win Tools (DPG Encoder)
Converting video to DPG
Now you need to extract the MoonShell Win Tools archive. This will contain an executable called dpgenc.exe this is the application that encodes videos to the DPG format.
Run this application and then set the language to the relevant one using the drop down box. Now choose your video(mpg/mpeg/avi/wmv) and click Start and choose the output location and the encoding should start. Video encoding time varies depending on the video and your PCs processer. On my Window XP system encoding is roughly half the time of the full video. Once converted copy the video to your DS flash card restart your DS and load Moonshell. Now navigate to the DPG video file on the top screen of your DS and press A.