I installed one IDE HDD and one IDE CD-ROM and use filo in etherboot . Filo recognize the IDE hdd as hda, and the Cd-rom as hdb.
in Config file I specify:
AUTOBOOT_FILE = "hdb:/isolinux/vmlinuz initrd=/isolinux/initrd.img expert nofb acpi=off devfs=nomount #ramdisk_size=65536 console=ttyS0,115200"

it installs OS well . it seems we don't need to specify CDROM to hdb1 .hdb works well.

bxshi