The Nintendo Wii has the ability to load home brew software that enables you to attach an external hard drive and play Wii ISO's or games from the drive. Prior to playing a Wii game from an external hard drive, you will need to have the Homebrew Channel with a cIOS, or custom Internal Operating System, installed. This will enable you to install a USB Loader program that loads Wii ISO's from external USB hard drives.
Navigate to the Google Codes download site to download USB Loader GX (see Resources). Click on the most recent .dol file to download. You may also download the most recent WAD file if you would like. WAD files are channels on the Wii main menu. Afterwards, navigate to the WBFS Manager website and click on "Download" to save the WBFS software to your computer. Install the WBFS Manager software by double-clicking on the set-up file and clicking "Next." Click "Next" when prompted and choose a directory to install the software to.
Plug the external hard drive into an available USB port on your computer.
Go to "My Computer," "Manage" and "Disk Management." If using Vista or Windows 7, go to "Control Panel," " Administrative Tools," "Computer Manager" and "Disk."
Right-click on the Wii hard drive and select "Delete Partition." After the deletion has completed, right-click on the Wii hard drive again and select "New." You can choose a new letter for your drive, choose not to format the whole drive or make your new formatted partition Primary and Active.
Open WBFS Manager and select your new Wii drive from the "Format" tab. Press the "Format" button to format your Wii drive into partitions that can be read by the Wii.
Click the "Browse" button in the lower right hand corner of the WBFS Manager program and locate the directory containing your Wii ISO image. Click on the Wii game to select it and click "Add Game" to copy the Wii game to your hard drive.
Insert an SD card into your computer and confirm its formatted for use with the Homebrew Channel on your Wii. Copy the USB Loader GX .dol file into a folder named USB Loader GX. The USB Loader GX folder should reside in the Apps folder so that the Homebrew Channel can recognise the application. You may also use a WAD manager to install the USB Loader GX channel if applicable, though it is not necessary for the USB Loader Gx program to operate.
Insert your SD card into your Wii once the USB Loader GX file has completed copying. Plug your external hard drive into the first USB slot closest to the edge of the Nintendo Wii.
Start your Wii and go to the Homebrew Channel. Select USB Loader GX and press "Load." Once USB Loader GX loads, the software will recognise your external hard drive and load your Wii games. Your Wii games are now ready to be played like a normal retail Wii disc.
Play your Wii game by selecting it from the main menu of USB Loader GX. Use the directional pad to move up or down or the Wii-mote to cycle the page list. Press "A" on the game you would like to play and "Start" to boot the Wii game.