You cannot—and should not—download a generic nand.bin from a website. Every Wii has unique encryption keys stored in its hardware. A NAND backup from one Wii will not work on another without significant, advanced modification. Attempting to "restore" someone else's NAND to your Wii is one of the fastest ways to your console (render it permanently unplayable). Why You MUST Create Your Own Backup
There’s no safe, legal, or functional shortcut. Spend 10 minutes dumping your own nand.bin . It’s easy, safe, and the only method that actually works. nand.bin wii download