@Effy
I had a 4,3 Gb hdd that couldn't be formatted on piss-se, so I hooked it up to my miggy, formatted, and got 4,3 Gb of space.. Not exactly what I expected - the very first cylinder of this hd was screwed up, that's why it couldn't be formatted under pc - but Amiga is great, so I moved RDB from sect 0 to sect 5 (the max sector for RDB is 7,[ might be wrong] but could cause some problems when set to it, so I used 5), and got fully usable, bootable hdd.. Ever tried moving RDB, maybe your disk is damaged the same way as mine..