Hi there --

I am trying to free up disk space in the / directory, and I noticed that the /lib/modules folder was the largest of all directories. The folder contains five kernel modules which are listed below:

2.4.18-18.7.x
2.4.18-18.7.xdebug
2.4.18-18.7.xsmp
2.4.18-3debug
2.4.18-3smp

I ran the uname -a command, and the output was the following:

Linux <hostname> 2.4.18-18.7.xmp #1 SMP <date> i686 unknown

My thinking is to remove the 2.4.18-3 kernels since that version is no longer being used on the system in question. What I am not sure about is if the 2.4.18-18.7.x kernel can be safely removed or should it be left alone. Can anyone clarify this? Thanks.

As far as I know, every directory that's contained in /lib/modules corresponds to a different kernel, and they should all be independent, so you could safely remove them.
Did you install them manually (make config, make deps, etc) or did you install them as a package with rpm, dpkg or whatever? If you installed them precompiled, I would deinstall them in the same way.
If you are not really sure to delete them, you can rename them (mv 2.4.18-18.7.xdebug 2.4.18-18.7.xdebug.old).