how to boot embedded system

Hi all

I build os for embedded target. I make initrd.gz file (using TOOLCHAIN/rootfs/).
And I put initrd.gz along with syslinux.cfg and vmlinuz (vmlinuz_2.6.21.7-dist) in CF(compact flash). At the time of booting its giving me error:
"Kernel panic - not syncing VFS: Unable to mount root fs on unknown block (0,0)."

how can I fix this problem?