This is a step backwards from the stable boot image at <http://ftp.us.debian.org/debian/dists/sarge/main/installer-i386/current//images/hd-media/boot.img.gz>. When I use that, it finds the ISO image just fine. All the drivers above, plus nls_cp437, get loaded without resorting to insmod. Of course it fails subsequently because the kernel version is different from the ISO image's.