I tried to update the kernel of installation CD to 2.6.15.6 too, but after that, I faced another problem: fbsplash.
If I use original initrd.img, fbsplash can't find the splash image to display; if I use initramfs, the ram disk is read-only, ie. can't run installation program which need read-write access.
After searching on internet, I found that I can use splash_geninitramfs to make the fbsplash things inside the kernel:
splash_geninitramfs -g usr/initramfs_data.cpio.gz -v -r 1024x768 --all
If run this command in the directory of kernel source, the fbsplash initramfs will be built inside the kernel, so I don't even need to update the initrd.img on the installation CD!
