The final numbers(2.6.20.6) is the version of you kernel. You can get this using uname -r (for the current kernel)
rm -rf /lib/modules/2.6.20.6 rm /boot/System.map-2.6.20.6 rm /boot/vmlinuz-2.6.20.6 rm /boot/initrd-2.6.20.6.img rm /boot/config-2.6.20.6
