Jython

Attempting to install Jython on a windows machine by typing the following 
in a command window:
java jython-21

The following errors appear:

C:\Jython>java jython-21
Exception in thread "main" java.lang.ClassFormatError: jython-21 (Bad mag
er)
         at java.lang.ClassLoader.defineClass0(Native Method)
         at java.lang.ClassLoader.defineClass(ClassLoader.java:502)
         at java.security.SecureClassLoader.defineClass(SecureClassLoader.
3)
         at java.net.URLClassLoader.defineClass(URLClassLoader.java:250)
         at java.net.URLClassLoader.access$100(URLClassLoader.java:54)
         at java.net.URLClassLoader$1.run(URLClassLoader.java:193)
         at java.security.AccessController.doPrivileged(Native Method)
         at java.net.URLClassLoader.findClass(URLClassLoader.java:186)
         at java.lang.ClassLoader.loadClass(ClassLoader.java:299)
         at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:265)
         at java.lang.ClassLoader.loadClass(ClassLoader.java:255)
         at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:315)

I am using java version 1.4.1_01

Thanks for any help you can give me on this.

-Mark Berlin