Removing old kernels that are not actually installed

[Colin Law]

I know how to remove old kernels by finding them in synaptic an
uninstalling them but I have a machine that has been through numerous
upgrades over the years and seems to have ended up with a number of
kernels in /boot that are found by update-grub but according to
synaptic are not installed.  For example:

~$ ls /boot/*2.6.27*
/boot/abi-2.6.27-11-generic         /boot/System.map-2.6.27-11-generic
/boot/config-2.6.27-11-generic      /boot/vmcoreinfo-2.6.27-11-generic
/boot/initrd.img-2.6.27-11-generic  /boot/vmlinuz-2.6.27-11-generic

Can I just remove all these files?

Colin