I just found one, complete in the package at Goodwill for $10. Brought it home, installed the software for code & firmware updates, and hooked her up to the PC (Windows 8).
The screen just sits there saying "Waiting for Nintendo DS".
I know it's not a hardware problem, because my PC clearly detects a device being plugged in when the USB cord is plugged in, makes the little jingle noise and everything.
I tried all the updates on CodeJunkies website. Then I had a whole new list of problems. Some were for the Action Replay DSi, and the only one I could find for the Action Replay DS was some code updates prominently featuring codes for the new Pokémon games. So I tried the DSi ones anyways, and still it didn't work, because the updates won't start installing until it detects the Nintendo DS, which is the problem.
So next I go and check the driver. Turns out that while the installation named a driver, when I go to update it, there actually isn't a driver there of any sort!
So then I start Googling the problem and the best answer I can find is to download the firmware updates, which like I explained won't update until the software detects my Nintendo DS! Yet it seems like this is a common problem, because I found a lot of discussion on it after Googling it.
Does anyone know of a solution to this problem that actually works?