The FMCB CD didn't work, but I found a FMCB DVD somewhere (and it appeared to be ESR patched), and it booted perfectly with SwapMagic. It booted LaunchELF, so I could install FMCB. I was indeed using DVD+R. Maybe this was the problem, I'm glad the FMCB DVD worked anyway.
It's solved, thank you...