I\'m using Launch4J to start my Java application and if an x64 JRE is present on the system, Launch4J seems to prefer it.
Unfortunately my application cannot run on
I had this exact problem about a year ago, using Lauch4J to wrap a small Java program that required a 32-bit DLL (swt-win32.dll, as it happened).
I found that if there were 32-bit and 64-bit JVMs installed, Launch4J would always favour the 64-bit one. It would only work if the 64-bit JVM was uninstalled, which was obviously not a practical solution.
I found no way of getting Launch4J to prefer (and require) the 32-bit JVM, after searching quite a bit and posting questions on its forum.
Therefore, I evaluated a good number of alternative JRE converters (I used this list: http://www.excelsior-usa.com/articles/java-to-exe.html).
I ended up settling on Jar2Exe, which was the only one that had the features I needed. It's not free, though there is an evaluation version, and I think it wasn't expensive.
Hope this helps!