I have tried compiling several gkrellm plugins, and I get the same error when compiling:

gcc -O2 -Wall -fPIC `pkg-config gtk+-2.0 --cflags` -g -c -o gkrellmlaunch.o gkrellmlaunch.c
gkrellmlaunch.c:36:30: gkrellm2/gkrellm.h: No such file or directory
gkrellmlaunch.c:43:2: #error This plugin requires GKrellM version >= 2
gkrellmlaunch.c:54: parse error before '*' token
gkrellmlaunch.c:54: warning: type defaults to `int' in declaration of `GKrellMLaunchInfo'

There is a lot more, but hesitate posting such a long error message, maybe this will help?

#error This plugin requires GKrellM version >= 2

Are you compiling Gkrellm2 plugins with Gkrellm (1) header/source files?

nope, I'm using gkrellm 2.1.1.4, and this is the first version of gkrellm i've compiled, so I shouldn't have any gkrellm1 headers, right?

Sounds right.
Which distro are you using? Cant you get .rpm packs if yours uses them? I have 2.1.15Mdk packs-links found on the GKrellm site.

I'm usiing Red Hat 9, and I installed Gkrellm2 with an rpm.
I did go to the gkrellm site to download v2 plugins, but they are not in rpm format, if this is what you mean. The package downloads do not include plugins.

This url was found by following the link on http://www.gkrellm.net to the RedHat packages, then RedHat9/Shrike, then Gkrellm plugins. Enjoy

Been there, done that. I found 2 plugins off the gkrellm site plugin section, namely gkrellmlaunch and gkrellmouse. These will not compile, and they are not included in the packages, because I installed the packages, and they are not in my plugin list.

Well the GKrellMouse site says it's not ported to Gkrellm2 yet.
GKrellMLaunch looks nice, but I cant find any good help files.

You do have the GKrellm devel source package installed, right?

I was never aware there was a GKrellm devel package. Thanks.