<p>I'd like to get at least one JRE/JDK level on my Windows machine where I have the JRE/JDK source that matches the exact level of the JRE/JDK. My purpose is to be able to go into the system classes while debugging. Any suggestions about how to do this? Thanks in advance.</p>

The source code is included in the JDK 1.5+ installer. Just make sure that the option is not unchecked while installing.