Java "sometimes" acts like Flash does (i.e. it does not update itself properly by simply installing a new version without un-installing the old one first).
1. Un-install any versions of Java you have on your system. Do a search of your system for any folders left over that relate to Java, delete them.
- if your brave do a search of your registry for "Java" and make sure the core keys for the old version are removed also (if you feel compfortable doing this).
2. Run a program like CCleaner to tidy up your system after you do this.
3. Download the latest version of JRE located here: http://java.sun.com/javase/downloads/index.jsp
- you really don't need the JDK version, the JRE is plenty (unless you are a developer).