Then you either don't have the Java development setup (SDK) installed, or you don't have your path set up to recognize it.
Do you get help text if you type just 'java' in the command window? If not, then you either do not have Java installed at all or don't have the path set up.
This
guide does not appear to talk about installing the core Java setup directly. It only mentions that you might need the Java JDK. It should specify that you need to have that installed first.
Go to
this page and get the Java JDK (use the SE 6 one). It will take a few steps, but then you should have Java installed and hopefully the rest of it will work for you.
Cheers,
Ancient Lady
AGK Community Tester