The PATH does not have anything to do with the location of Java class files. The PATH is an environment variable used by the operating system to find programs to run. In your other topic we already answered your question about how to set the PATH.
You need to add the bin directory of your JDK installation to the PATH. So, for example, if you have installed the JDK in C:\Program Files\Java\jdk1.7.0_07, then you have to add C:\Program Files\Java\jdk1.7.0_07\bin to the PATH.