doc.FAQ.HowDoIInterpretClasspaths Was CLASSPATH set at the time of reported failure? Review the output of set, the Windows autoexec.bat file, or Windows System utility screen-shots for corroboration. Does CLASSPATH point to a valid .jar file? Review the output of ls or dir in the directory structure for the purpose of corroboration. Do file or directory permissions issues restrict access to the .jar file? Does the .jar file JDK version correspond with the client JRE version? Does CLASSPATH need to be set within application code?