good question! so how would i find this? and what actually determines the OS? it would appear (to me) that the main install package is plesk (panel) which i use for certain functions, domain admin etc, with fedora core4, which i assume is the linux/unix bit???

Plesk is just the admin tool for your environment your provider gives you, like Confixx etc etc etc.
Fedora Core 4 is a Linux distribution, yes. It should have rpm and yum which you can test by running the command "which rpm" or "which yum" or just type in the commands without "which".

i decided to go with this instruction (having already researched yum and rpm etc somewhat) but lets assume i used the man pages on this ocassion, and yum seems to be the simplest and user friendly method.
this resulted in a very quick and "completed" install.
i was hoping to keep this a simple "step by step" exercise, however it is now getting very complicated.
yum has installed/updated version ImageMagick-6.2.5.4, which i suspect was part of origional server setup, however, having already "played", (and installed version ImageMagick-6.4.1) it would seem i have 2 versions installed. should i have first checked if there was "any" version installed.
i also notice (from my previous efforts), that this install has taken some instructions from 6.4.1 ... example "./configure --enable-shared --with-perl --disable-openmp", which is not the default.
my head is hurting again...
neither version is working (for what i want it to do, which is work with jpegs).
i feel i need to jump ahead here....
but will wait some comments for now...

It doesn't work might produce an error output - posting that might help too, as our webcam in your back is not adjusted very well.

You can also wipe the installation and reinstall it anew.

If you want to know if you have 2 installations or something like that, do a
and check the output.