I asume that MEPIS uses the same startup method as Debian, because it is built on it. This method is called System V. Here is some info
http://www.freeos.com/articles/3243/...SSID=d6428594c. Basicaly you should search for some utility in your distribution that does all the managment with theses startup scripts.
You could also search for file named S*pppoe* in your /etc/init.d/... or /etc/rc.d/init.d/...
Startup scripts are executed in each runlevel. If script starts with letter "S" it is started (i guess that means it is executed with option "start"), if with letter "K" - stopped. Scripts for each runlevel are located in subdirectory for that runlevel (that is for example /etc/init.d/rc5.d/ or similar for 5th runlevel). Usualy there all scripts are in one directory, but in subirectories you have symlinks with "S" or "K" prepended to their names.
Thats all I could recall about these ...