Go to:
java.sun.com/products/plugin/downloads/index.html

You will see:

"The above default release, 1.4, is the latest release of Java Plug-in. sun  recommends that you use it. However, if for some reason you need an older release, such as 1.3.0, 1.3.0_01, 1.3.0_02, or 1.3.1, they are available from the link below. Note that you should always download  and use the corresponding version  of the html  Converter for any of the 1.3.0 releases of Java Plug-in. (In 1.4, the converter  is included with the SDK 1.4 Standard Edition release.)"

So, if you are still willing to download any of the older versions, just try this out:
http://java.sun.com/products/archive/