If you don't have an FMCB memory card, or you happen to corrupt yours (like I did), you can use FHDB (FMCB's brother on the HDD) to boot uLauncher, then reinstall FMCB on your card.
Using a HDD to boot a PlayStation requires that you write a custom MBR on it.
As far as I've seen, there are many mbr images on the internet, but not all of them work with the Game Star network adapter.
The image I used and that worked for me is __mbr.raw, that you can find in this archive.