The Wii is a video game console made by Nintendo that was released in 2006. The Wii uses motion sensor controllers to allow you to move as you play games, making the games more interactive. The Wii is capable of playing certain video formats, such as MKV, but it has to be hacked and running a custom media play program to do so.
Open up your web browser, and navigate to the Homebrew Browser download site (see Resources).
Download the Homebrew Browser package by clicking on the word "Here" under the word "Download."
Extract the download by right-clicking on it and selecting "Extract All."
Click the "Next" button in the unzip wizard, and select the "Finish" button when it is done extracting your file.
Insert your SD card into your computer (via a USB card reader or a built-in SD card port), and in the auto-play options that appear, double-click on the words "Open folder to view files."
Click inside the new window that appears displaying the contents of your SD card with the right mouse button. Select "New" and then "Folder."
Title the new folder "apps," and open it.
Minimise the window displaying the contents of the folder "apps," and navigate back to where you downloaded the Homebrew Browser folder.
Click on the folder you extracted in Step 2 with the right mouse button, and select "Copy."
Maximise the window displaying the contents of your "apps" folder.
Right-click anywhere inside your "apps" folder, and select "Paste."
Wait for the Homebrew Browser folder to be copied to your SD card. Use the same copy/paste technique to move your MKV file to your SD card.
Remove your SD card from the computer, and insert it into the Wii.
Turn the Wii on, and select the "Homebrew Channel" from the main menu screen.
Select "Homebrew Browser" within the Homebrew Channel.
Click the "Load" button, and wait for the Wii to connect to the Internet and load your Homebrew Browser.
Select the "Media" menu, and scroll down until you see an app labelled "GeeXbox." Select it, and click the "Download" button.
Wait for the app to download, and when it finishes, tap the "Home" button in the middle of the Wii.
Click the "Return to Loader" button. This will take you back to the Homebrew Channel.
Select the "GeeXbox" app, and click the "Load" button.
Press "1" and "2" to connect the Wiimote to this program.
Press the D-Pad on the Wiimote (any direction), and select "Open."
Use the screen that appears to find your MKV file on your SD card, and highlight it with the selector.
Press the "A" button, and GeeXbox will play your MKV file.