Hi,
You can use JNative to enumerate all windows ; see http://jnative.cvs.sourceforge.net/jnative/JNative/src/java/JNative/org/xvolks/test/callbacks/EnumCallback.java?view=markup
then knowing the HWND post a WM_QUIT message.
You can also use the PsApi class to kill the process.
--Marc (http://jnative.sf.net)