In order to compile and run HelloWorld project change classpath in the 
project properties dialog.
1. To make the project compilable add %WL_HOME%\lib\weblogicaux.jar or 
   %J2EE_HOME%\lib\j2ee.jar .
2. %WL_HOME%\lib\weblogicaux.jar, %WL_HOME%\classes are necessary to run the client.
   Also, you should add path %J2EE_HOME%\nativelib in your PATH environment variable 
   (it's a path to ioser12.dll). 

%WL_HOME% - home directory of Weblogic Server (e.g. c:\wls51)
%J2EE_HOME% - home directory of J2EE (e.g. c:\j2sdkee1.2).

Add necessary libraries:
- Select 'MainMenu|File|Project Properties'.
- In the opened dialog select 'Search/Classpath' page on the 'Resources' pane. At this moment nothing should be added to the classpath.
- Press 'Add Zip/JAR' button and add %WL_HOME%\lib\weblogicaux.jar.
- Press 'Add Path' button and add %WL_HOME%\classes.
- Press 'OK' button to save the project properties.

Note: weblogicaux.jar should stay previously to all libraries. 
