it could also mean that his sd card is not compatible...
You beat me to it. =)
Anyway, from
bootmii.org/faq:QUOTEI installed BootMii/boot2, but it doesn't come up when I boot my Wii.
Try booting with no SD card inserted. If you see a brief set of flashes from the blue slot LED right after you hit the power button, try a different SD card. Make sure you have a directory named "bootmii" with the "armboot.bin" and "ppcboot.elf" files inside.
If you do not see those flashes, BootMii/boot2 is not installed.