Installing Java 1.4.1 on Ubuntu 9.10 (Karmic Koala) turned out to be nothing but a pain.
Firstly, Java 1.4.1 has now reached End of Life, so Sun doesn't support it any longer.
1. So, download Java 1.4.2_07 from the archive: http://java.sun.com/products/archive/j2se/1.4.1_07/
2. Then when you try to set the file to executable by 'chmod -x' and then run it, you're likely to get an error message like:
"tail: cannot open `+341' for reading: No such file or directory"
Then something about the download being corrupt.
This is because (according to here) the tail program in Linux has changed slightly since then and has a different syntax.
To get around this, I unzipped the .bin file using 7Zip on a Windows system; but I guess p7zip can be used on a Linux system too.
3. Then I placed the 'j2re1.4.1_07' folder into my /usr/lib/jvm/ folder and did the procedures 5 to 6 as in the previous post.
4. Then finally, manually added the plugin (so that it works in Firefox) to the list of plugins as given in the 'Java Applet Runtime Settings' -> 'View' in the GUI for the ControlPanel command.