How to find JRE Version on client machine

Question

My client machine does not have any class file, they are running web pages on web Browser.
We have some specific plug-in based on JRE Versions (e.g. JRE 5 or JRE 6).
Also we do not have permission to run an applet on client machine as it�s a security concern.
We have following senerio
Application server on Machine-1
Web Server on Machine-2
Client on Machine-3
We need JRE version of Machine-3.
Please provide me a solution.
Thanks in advanced.

Answer 1

Old post but replying anyways so that the solution can be used for later
For Firefox/Mozilla/Netscape this can be done through javascript like below
     for (i=0; i<navigator.plugins.length; i++) {
     document.write(navigator.plugins.name);
     document.write("::::");
     document.write(navigator.plugins[i].filename);
     document.write("::::");
     document.write(navigator.plugins[i].description);
     document.write("<p>");
It prints out "Java Plug-in::::NPJava12.dll::::Java Plug-in 1.4.1_02 for Netscape Navigator (DLL Helper)"
from which the plug-in version can be found out
For IE :
     try{
          var obj= new ActiveXObject("WScript.Shell");
          if (obj!= null) {
//Version for the installed JRE          
var ver = shell.regRead("HKEY_LOCAL_MACHINE\\Software\\JavaSoft\\Java\ Runtime\ Environment\\CurrentVersion");
          alert(ver);
     }catch(e){}