After you have created or downloaded a zImage, you should install it.
# cp /boot/zImage.initrd-2.6.18-28.el5 /mnt/tftp_zImages/If you downloaded the zImage for Fedora 7, type for example:
# cp /boot/zImage.initrd-2.6.22-5.20070920bsc /mnt/tftp_zImages/Ensure that the zImage file name matches the one configured in DHCP.