While installing the new VMware guest program on my Xubuntu VM I noticed the installer working on a large number of old and kernel files. I tried to get the number of old kernels and remove them by script.
There is a nice script to automatically remove old kernels and retain the two latest kernels: purge-old-kernels
After installing you can call the script
To see old kernel files:
dpkg -l | grep linux-image-
To see the currently used kernel:
Here is a screenshot of how it actually works: