You may not want to change the CLASSPATH environment variable for your computer perhaps because there is a Java application installed and you do not want to tamper with that. So you can change the CLASSPATH environment variable on a session basis in a few ways. These instructions may not apply if you are using a development tool but certainly apply if you are using the operating system command prompt.Setting the class path -- http://java.sun.com/j2se/1.4.2/docs/tooldocs/windows/classpath.html