He's in over his head and doesn't know the command line very well. So he doesn't know how to do:
set JAVA_HOME=somepath
set PATH=somepath;%PATH%
on the command line. And my guess is that he set the global one (or something like it) to the wrong place... which can mess up Java.
It's ok to set those so you don't have to do it on the command line every time you want to run them but you have to get them right or, as you say, bad things happen.
As you say, I am way over my head. everyone i believe was like that at one time. i don't think you (Paul) have never done something bad like this in a way.
Everyone has to start somewhere. Though most people tend to ask for tool support with the tool vendor and not some random semi-related forum...
I learned on DOS. Environment variables are a way of life. But it's fundamental stuff. Maybe you should spend some time learning how to right batch files.
and Paul, once this is fixed (hopefully fixable) i won't bug you for a week

i realize i have been consuming your time majorly.
Uninstall all of your Javas.
Open a command line.
Type: java -version
confirm that it tells you "command not found"
Install the JDK
Open a new command line.
Type: java -version
confirm that it runs and tells you the version
Run the Mythruna .exe