Wii game discs use a special file format that the Wii's disc drive can read but a computer's disc drive cannot. You can read the data off of a Wii game disc on your computer's disc drive by using a Wii copy program. The Wii copy program will let your PC's disc drive read the data off of the Wii game disc and transfer it to the computer's hard drive. The backup that has been made from the Wii game disc can then be archived or burnt onto a DVD to use if you want to put the original Wii game disc away. Using a Wii copy program to read a Wii game disc on your PC is not illegal to do.
Download a Wii copy program to the PC's desktop, like the CopyThatGame Wii copy program (see the link in Resources). Double-click on the icon of the Wii copy program when it has fully downloaded. Follow the menu prompts to install the Wii copy program to the PC's hard drive. Restart the PC after the installation is finished.
Eject the disc tray of the DVD/CD-ROM disc drive. Put the Wii game disc onto the disc tray. Close the disc tray.
Run the Wii copy program. Select the DVD/CD-ROM drive from the "Devices" drop down menu on the Wii copy program's main screen.
Click on the "Browse" button next to the "Save To" tab on the Wii copy program's main screen. Navigate in the window that appears to the PC's desktop. Click the "OK" button to close the window.
Click on the "Copy" button on the Wii copy program's main screen. Wait as the PC reads the Wii game disc and makes a copy of it on the hard drive. Quit the Wii copy program when the copy has been made. Eject the disc tray and remove the Wii game disc.
You can save the backup Wii game on the computer's hard drive and burn it to a disc only if the original Wii game disc has a problem.
Making a copy of a Wii game that is not your personal property is piracy.