@Arenas:
I strongly recommend against decompiling EXEs. In many ways, it's illegal. The only way I can see it NOT being illegal is if it's your own EXE that you're decompiling.
Next on the list, you have set up the compiler incorrectly for compiling the FPSC source code. Chances are that you upgraded to the latest version of DBP, in which case, you're not likely to be able to compile the source code.
I'm still not sure WHY you want to "decompile" something. You stated that you wanted it in DBP format, which is what the upgrade extras GAVE you.
From what I remember, most everyone who decided to Mod the engine had a lot of troubles getting it to compile correctly. It's just something you're going to have to work through.
[EDIT]
FYI, the DBP libraries are written in C++, so if a decompiler had to choose between the two.... I'd go with C++ also.
[/EDIT]
The one and only,