Action Replay is a cheating company from Canada. Now, the codes may seem just a bunch of numbers and letters, but it's addresses and codes. Here's an example. In SM64DS, there's this code- 020988a4. 020988a4 is the address of the code, while 00000033 is the value of the code. Action Replay has a bunch of letters and numbers, and you can format your Action Replay in so many ways. If you format your AR, then you probably try to insert the same games. But when you do, these red & blue lines show on the touch screen. Here's how to be able to write codes and Game ID's- hold START+SELECT then turn your DS on. Then, before the screen says "This product is not liscenced by Nintendo, press A+B. Now you can!! And there's a D2000000 code. you don't nesessarily need them for addresses that start with 1,2,or 0, but it help prevent the AR from glitching. Action Replay has several volumes. Only certain games are for the certain volumes. You can type the Game ID in, put in a couple codes, then the Action Replay formats itself because the game you typed wasn't for that particular volume. If the Action Replay says "unknown game", then don't bother with that game. Now you can enter different codes for a game that's already on there, no harm. Action Replay has this secret thing that has to do with England's Codes 4 Life. If you take the AR cord and plug it in to the computer and DS with a C4L disc in the computer ROM, then you can seriously damage, depending on how many times it's been formatted. If it's been erased 3 or more times, then arely any harm will contact. On the computer screen, it'll pop open to C4L and you can select a game and drag it to the AR section. Then if you want to see the addresses and values of C4L codes, make sure you do it on the PC. NOT THE ACTION REPLAY!!!! Or your DS will not munfunction correctly. But Action Replay has codes that you put in that are not on the Aciton Replay already, like this one- 0204xxxx. This is a good address for beginners because you only have to remember 0204! This code is a Super Mario 64 DS code, it changes the color texture of stuff. And the value is not hard to remember, it's 00000000. You can put different numbers and letters after 0204, and see what happens! Action Replay does NOT hack into the game system. Action Replay DS is fairly simple to use. Once you start using it, I think you'll get the hang of it.