A friend has a softmoded Wii with the HBC already installed.
He can't run the HBC because he doesn't have the sd card with the necessary file installed.
Is there a way to get HBC working so he can install a usb loader?
HBC does not rely on an SD card, in fact it loads files from the SD card. HBC is a Wii NAND resident channel or application.
If HBC is installed properly it'll start up with a little bit of music and load to a screen with bubbles, or files.
If you wish to install a USB loader you need to get the relevant files and put them in an apps folder onthe SD card. i.e. sd:\apps\usbloadergx\boot.dol
Not really doing much Wii stuff these days.