If you want to clean up your system, and
free some space on your system partiton, removing old unused kernel
versions is a good start.
NOTE: Before starting any of this, make
sure you have a solid back-up (There are several good GUI driven back-up
systems for Linux available, although I still like to run my own
scripts using rsync)
1. find out what the current kernel version is (open a Terminal screen):
uname -r
2. Do a test run and see what will be removed. (nothing will actually be removed. it is so called a dry - run command)