Izpack fails with 'There is no script engine for file extension ".js",

There are four questions asked here:

1. Why is 32bit exe working and 64 bit exe not working
2. Why does neither 32bit or 64bit if I try and install without the wrapper.
3. Why does simply associating filetype with an editor break this javascript stuff, I can imagine that this or a similar problem could effect alot of users.
4. Why would running from my 64 bit wrapper cause installer.js to run Abort Exit

I will attempt to answer them:

1. Errors and bugs sometimes in programs that are supposed to 'seamlessly' handle both 32- and 64-bit; one example is Symantec's SEP definition repair program - it works sometimes but not all. Your comment confirms these bugs, and you've even identified a competing program that does not error in this 32/64 handling: "Haven't solved this problem but have worked around it by running the installer using launch4j instead of winrun4j". Congrats! :)

2. I suspect the requisite app/wrapper is not in your system's PATH. Two folders in your path are C:\WINDOWS, and C:\WINDOWS\SYSTEM32. At the command prompt, type the word SET (caps not needed). An alphabetically-sorted list of variables appear. In the one that says PATH= look for the full folder path of wrapper that you expect to launch your app. It's likely not there. It can be added if you like.

3. Good question, but there's a good reason: by associating a filetype to open with a program, you're telling your computer to always open the file, in this case ending with .js, with a file editor. It's doing what you told it to do, not what you intended. A popular way to get what you intended is to re-associate the file with the program it had before (you would likely know which one is best), and to edit the file, add your favorite JS editor to the "Open With..." option in Windows Explorer's right-click menu. I can find and link to a page or two on how to do this, if you like.

4. I believe this is strongly tied to question and answer #1.

Let me know if this helps.

Changing the default action for .js files causes problems for the same reason that changing the default action for .exe files would cause problems. Programs expect that the default action for another program will be to run it. Editing should always be a right-click action and not the default.