Lifehacker
Lifehacker reader Mike put together a tutorial on enabling hard-drive-based playback on your Wii. It isn't as simple as just plugging in an external USB drive, but if you're comfortable messing around with your Wii, it also isn't an impossibly geeky task. You need to have the Homebrew Channel installed. We've covered how to install the Homebrew Channel here before, but console modding is an ever-changing business, so make sure to give Mike's tutorial a full read before proceeding. Besides the Homebrew Channel, all you'll need is an external USB 2.0 hard drive and freely available files listed in the tutorial. When it's said and done, you'll likely be the only one on the block—or in your city for that matter—with a hard-drive-driven Wii. Check out the video below to see the interface in action—Spawn-based skin mod not included:
Lifehacker article
Mike's instructions
Youtube video