Running Kubuntu on a laptop that I occasionally dual-boot to Windoze XP. Over time the GRUB menu had filled up with old Linux kernal versions. A search revealed that cleaning it out was a bit more complex than I was hoping for but not too tricky and it worked. There may be better ways to do this, but this worked for me:

1. In a terminal window execute “sudo update-grub” to rebuild the list. This displayed a list of versions installed.
2. Using KPackageKit from the menu search for “linux-image”. Lists the installed packages marked with X (can be uninstalled).
3. Uninstall all but the current version (33) and the one before (32)
4. Re-run “sudo update-grub” to rebuild the GRUB menu

All done.