What you're asking about is called a disassembler. It won't help you very much though. Most of what makes a source program useful is the comments and the names for variables and instruction labels. None of that can be recreated from the hex code. Depending on the processor (if not an SX), there's no guarantee the output of a disassembler will be able to be assembled and run successfully.
Comments
Here's a link for one disassembler for the SX: online.dip.jp/angelica/index_e.html
Post Edited (Mike Green) : 12/5/2008 10:20:34 PM GMT