Ok, I've decided it's probably easier to wipe the whole thing and start again. So I need to get back into EM mode, but this
suggests that setting the "NGNGNG" flag in the flash is somewhat risky if I don't know what I'm doing, especially as I'm not entirely sure what kernel version I'm actually running now.
I figure that it would be easier to completely blank the drive. Can I do this without removing the HD? Is simply deleting all the files and rebooting good enough, or do I somehow need to scrub the partitions too (and is this even possible while I'm running the system in the first place?)