Comment 10 for bug 300773

I have a similar problem on Mint 18/Ubuntu 16:

sudo apt-get purge linux-image-4.4.0-xx-generic linux-headers-4.4.0-xx

and it shows the message: dpkg: warning: while removing linux-image-4.4.0-xx-generic, directory '/lib/modules/4.4.0-xx-generic' not empty so not removed

In /lib/modules/
4.4.0-21-generic 4.4.0-45-generic 4.4.0-62-generic
4.4.0-34-generic 4.4.0-47-generic 4.4.0-64-generic
4.4.0-36-generic 4.4.0-59-generic 4.4.0-66-generic

and in ever such dirs there is only the subdir updates with inside:
vboxguest.ko vboxsf.ko vboxvideo.ko