Success. Here's what I did: ********************************************************** * in archiso2dual, change isohybrid -offset 1 "${imagename}" to: isohybrid "${imagename}" ********************************************************** * mastered my own i686 and x86_64 ISOs, combined them into dual ISO with: sudo archiso2dual -T full -3 myarch-2010.03.22-i686.iso -6 \ myarch-2010.03.22-x86_64.iso -o myarch-2010.03.22-dual.iso -y * wrote to my USB key (/dev/sdc) using: sudo dd if=iso-mine/myarch-2010.03.22-dual.iso of=/dev/sdc bs=8M * created a second partition, starting with sudo fdisk /dev/sdc ... fdisk turns out to be not very hard, especially if one has used cfdisk. Googling "fdisk howto" may help. * create filesystem on second partition, with a label: sudo mkdosfs -F32 -nmylabel /dev/sdc2 At this point, both /dev/sdc1 and /dev/sdc2 are mountable. Plus I can boot from the USB key and login successfully. (When testing, don't just check for bootability, see whether you can get all the way to a login prompt.) I can also mount /dev/sdc2 when I've booted from /dev/sdc1. So it looks like everything is now working properly... Still, I wouldn't mind getting some more clarification about the offset=1 vs offset=0, and the limits/snags of using hybrid ISOs. I get the impression these are still something of a moving target. -- Jim Pryor profjim@jimpryor.net