Error in kernel compilation

I have compiled the following two kernels enabling the NTFS module & other modules as it is on RHEL5. All cmd run successfully.

2.6.18.8 & 2.6.35

at the time of creating the initrd image, with the respective cmd, the following error pops-up

For the kernel 2.6.18.8

Cmd: -mkinitrd /boot/initrd-2.6.18.8.img 2.6.18.8
Error:- No module ata_piix found for kernel 2.6.18.8, aborting.

For the kernel 2.6.35

Cmd:- mkinitrd /boot/initrd-2.6.35.img 2.6.35
Error_ No module ehci-hcd found for kernel 2.6.35, aborting.

The following Kernels module are in lib/modules dir.

ls /lib/modules/

2.6.18.8 2.6.18-92.el5 2.6.