Old Firmware
If you have old firmware or a version of Action Replay that came out before "Pokemon Pearl," it won't recognize the game. Your Action Replay came with a disc that includes PC software, allowing you to connect your Action Replay to your PC for updating and editing codes. This program also makes it easy to download the latest codes from CodeJunkies.com, the official website for Action Replay cheats. Once you install the software and update your Action Replay's firmware, you should be able to use it in conjunction with "Pokemon Pearl" as easily as any other game.
Installing the Software
Insert the Action Replay software disc into your computer and follow the onscreen instructions to install the software. After installation, insert the Action Replay into your DS and plug it into your computer using the USB cable that came with the cheating device. Windows automatically detects that you've attached something new to the computer and asks you where to find the drivers for the new device. Direct Windows toward the main folder of the Action Replay CD and Windows will do the rest.
Upgrading Firmware
With the Action Replay connected to your computer and the code manager software open, click "Software Update" near the top-right corner of the program's window. Ensure your computer is connected to the Internet so the program can download the updates. When the software informs you there's new firmware, confirm that you want to install it. Do not perform the upgrade while your DS' batteries are low and do not disconnect the DS or Acton Replay while the firmware updates. When finished, restart your Nintendo DS, finishing the process. Insert "Pokemon Pearl" into the Action Replay and see if it recognizes the game.
Entering the Game Manually
If the Nintendo DS still says "Unknown Game" when you insert "Pokemon Pearl," write down the code directly under "Unknown Game." Using the PC software, navigate to the "My Codelists" section and opt to create a new list. Find the CodeJunkies website under your "My Subscriptions" list and locate "Pokemon Pearl" within that codelist. Drag and drop "Pokemon Pearl" from the "My Subscriptions" section into your new codelist. Drag the codelist to your computer's desktop and open it with Notepad. Find all instances of the "<gameid>" tags, where you'll see the serial number for the game. Replace the serial number with the one you wrote down earlier, save the file and close Notepad. Drag the codelist back into the code manager software's "My Codelists" section. Press the "Quick Codelist Update" button next to the "Software Update" button you used to update the firmware.