i doubt the kernel is at fault there
my comp has 3 kernels installed, between the contents of my /boot partition and /lib/modules it is < 300 megs combined for ALL 3
but if you need to get rid of an older kernel, simply remove the entry in /boot/grub.conf (or menu.lst, which i find is often just a symlink to grub.conf anyways, remove the relevant vmlinux,System.map, and initrd files, then remove the relevant directory from /lib/modules
or if it was installed using the system's package manager just use the package manager's 'uninstall' feature
although imho this seems pointless because the slight increase in space doesn't seem to me to justify sacrificing having a 'lifeboat' handy in case something goes wrong with your current kernel
fedora seems to leave 3 or 4 versions of the kernel installed 'just in case'
as they say, fortune favours the prepared mind