How can I build a jar for a previous Java version?

I am trying to compile my code and run it on a different server. The problem is my JRE version is Java version "1.6.0_13" and that on the server is Java version "1.4.2".

This gives me "unrecognized class file version" exception when I try to run the jar on the server. I cannot compile my code on the server because of various dependencies I will have to set up.

So I need to know if there is a way to "use Eclipse" [this is easier than command line since it takes care of dependencies] and compile my stuff using 1.4.2 instead 1.6.0_13. Do I have to uninstall my JRE from my machine, then reinstall previous version and then compile or is there an elegant and cleaner way?