how do I download Action Replay to my Nintendo DS?
Go to this link: http://unknown.hcs64.com/ards/AR_v1.0.zip
You need a ds flash card to run it on your ds. (or install wifime on your pc to get it through download play)
An other alternative is to download nitrohax, its an Action Replay DS clone and its ds homebrew (which means its free) http://www.youtube.com/watch?v=ZnGaq4GFJLA
I'm not going to help you illegally download a game, but I will tell you that there are half a dozen or so used games on Amazon for 20 bucks.