Raw ISO files are large and not optimal for USB loaders. Most users convert to WBFS format or use a FAT32 drive with split files.
To play ISO files, you must first install the Homebrew Channel. If you already have this, skip to Step 2. play wii iso on wii
You can run WiiWare and Virtual Console games directly from your USB drive. In USB Loader GX, go to Features > Dump NAND to USB. Then, install your WiiWare WAD files. This saves precious internal memory. Raw ISO files are large and not optimal for USB loaders