From AskUbuntu,\\

In Terminal, type
<code>
sudo apt-get remove --purge $(dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d')
</code>


or using Synaptic\\
First find your latest kernel by typing
<code>uname -r</code>
Search for **linux-image**, right-click a kernel (not your current one) and choose ''Mark for Complete Removal'' and finally click the ''Apply'' button to delete the kernel.\\
Similarly do the same for **linux-headers.**\\

DO NOT remove your current kernel, you will make your system UNBOOTABLE!