How to open protected MRS files?

Hey,

I got old files from my old private server but my friend, the developer, made those files and protected them so I can´t open them and others who aren't allowed to open them.

So my questions are:
1. What decompiler do I use?
2. How do I find out that code to open it?
3. How do I use the code?

Questions such as that, if you can help me.
Please reply below!

Thanks!

I'm currently using this MRS (De-)compiler:
http://i55.tinypic.com/wchbtt.png