In order for HBC to detect IOS58, the IOS has to be already installed when you install/update your HBC.
If you installed IOS58 after installing/updating HBC that is why it can not see it.
You do need indeed to reinstall your HBC in order for it to make use of IOS58, and you are right, there is no such 're-update' feature. However, you don't need to use a exploit again to run the HackMii installer, just copy the boot.elf file into a folder inside sd:\apps (for example sd:\apps\hbc_update) and you can launch the installer from your current HBC itself.
I hope this helps you to solve your issue.
Edited 1 time(s). Last edit at 10/14/2010 04:01PM by Axel.