To enable DVD playback, you will need to install software to the Wii. The software uses an exploit, which is a security flaw, in the Wii's coding in order to make the Wii run unlicensed code. To do this may void your Wii's warranty, and you should only do so if you are confident that you know what you are doing.
The easiest way to install the software uses nothing more than the Wii and an SD card along with the HackMii installer. Bypassing these restrictions is not illegal in the U.S. for "homebrew" software, but using them to play copyright-protected video games is.Learn more about Gaming Consoles