From Existing BootMii

If you already have BootMii installed and you want to install the HBC, update the HBC, or reinstall BootMii then here's how to do it.
Download:
The HackMii Installer v1.2 (if you don't have it already)
What you need:
- BootMii on your Wii (of course)
- SD card (or SDHC) formatted as FAT16 or FAT32. (You should already have one for BootMii anyway)
- SD card reader for PC or a PC with one built-in. (Cameras or other devices can work)
- The newest version of the HackMii Installer
Guide:
- Take the HackMii Installer "bootmini.elf" and copy it to your SD card
- Run BootMii and select the SD icon using a Gamecube controller or the Power button on the front of your Wii and select it by pressing A (with a GC controller) or the Reset button on your Wii
- Find "bootmini.elf and select it by pressing Reset
Note: It is very common that using the above method won't work and causes a "green screen" when you try to run it. To get around this do the following:
- In the "bootmii" folder on the SD card, find "ppcboot.elf" and rename it to something else (such as "bootmiippcboot.elf")
- Take the "bootmini.elf" and rename it to "ppcboot.elf"
- Copy the HackMii Installer's newly renamed "ppcboot.elf" into the "bootmii" folder
- Put the SD card in your Wii and turn it on
- It should load the HackMii Installer automatically