This is available, free, from Sun at
http://java.sun.com/j2se/1.3/jre/index.html
Also, make sure that Java is enabled in your browser preference settings.
In IE, select Tools > Internet Options > Advanced.
Scroll down the list
of Settings until you find Java VM.
Be sure that 'JIT compiler for virtual machine' is selected.
In Netscape, select Edit > Preferences > Enable Java