Force Internet Explorer to use a specific Java Runtime Environment install?

First, disable the currently installed version of Java. To do this, go to Control Panel > Java > Advanced > Default Java for Browsers and uncheck Microsoft Internet Explorer.

Next, enable the version of Java you want to use instead. To do this, go to (for example) C:\Program Files\Java\jre1.5.0_15\bin (where jre1.5.0_15 is the version of Java you want to use), and run javacpl.exe. Go to Advanced > Default Java for Browsers and check Microsoft Internet Explorer.

To get your old version of Java back you need to reverse these steps.

Note that in older versions of Java, Default Java for Browsers is called <APPLET> Tag Support (but the effect is the same).

The good thing about this method is that it doesn't affect other browsers, and doesn't affect the default system JRE.

For the server-side solution (which your question was originally ambiguous about), this page at sun lists one way to specify a JRE. Specifically,

<OBJECT 
  classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
  width="200" height="200">
  <PARAM name="code" value="Applet1.class">
</OBJECT>

The classid attribute identifies which version of Java Plug-in to use.

Following is an alternative form of the classid attribute:

classid="clsid:CAFEEFAC-xxxx-yyyy-zzzz-ABCDEFFEDCBA"

In this form, "xxxx", "yyyy", and "zzzz" are four-digit numbers that identify the specific version of Java Plug-in to be used.

For example, to use Java Plug-in version 1.5.0, you specify:

classid="clsid:CAFEEFAC-0015-0000-0000-ABCDEFFEDCBA"

I'd give all the responses here a try first. But I wanted to just throw in what I do, just in case these do not work for you.

I've tried to solve the same problem you're having before, and in the end, what I decided on doing is to have only one JRE installed on my system at a given time. I do have about 10 different JDKs (1.3 through 1.6, and from various vendors - Sun, Oracle, IBM), since I do need it for development, but only one standalone JRE.

This has worked for me on my Windows 2000 + IE 6 computer at home, as well as my Windows XP + Multiple IE computer at work.

Use the deployment Toolkit's deployJava.js (though this ensures a minimum version, rather than a specific version)

If you mean when you are not the person writing the web page, then you could disable the add ons you do not wish to use with the Manage Add-Ons IE Options screen added in Win XP SP2