Question

I installed JRE 6 on my existing 1.4.2 causing some applets in IE6 requiring 1.4.2 to stop working, how can i revert this back without uninstalling JRE6?

Answer 1

How do you deploy your applet? I assume you are using a jnlp file descriptor (Java Web Start).
If so, maybe you find this link useful:

http://docs.oracle.com/javase/1.5.0/docs/guide/javaws/developersguide/syntax.html

You can use this advice when deploying:
http://docs.oracle.com/javase/6/docs/technotes/guides/jweb/deployment_advice.html

As far as I know, the standard in deploying applets nowadays is to use the deployJava script AND a jnlp file. This way you can detect the client’s jre’s using

getJREs()

Choose the appropriate one and then initiate your applet by calling:

runApplet(attributes, parameters, minimumVersion)

Please take in account that depending on the Java Plugin the client runs, above approach might not work. DeployJava gives you an option to handle that

To deploy an applet that runs on the old and new Java Plug-ins,
specify the applet tag attributes and JNLP parameters as shown in the
example below:

var attributes = {codebase:'http://java.sun.com/products/plugin/1.5.0/demos/jfc/Java2D',
                      code:'java2d.Java2DemoApplet.class', archive:'Java2Demo.jar', width:710, height:540} ; 
var parameters = {fontSize:16, jnlp_href:'java2d.jnlp'} ; 
var version = '1.6' ; 
deployJava.runApplet(attributes, parameters, version);