Just run this command to clean up any old kernels having about on my system;
dpkg -l pve-kernel-* | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"` | grep -e [0-9] | xargs sudo apt-get purge
found it here; https://pve.proxmox.com/pipermail/pve-user/2013-October/162779.html
and...