Exe to source code

A program written by someone who has since left the company is not doing quite what we thought it was supposed to do.

I've been asked to try and decompile the program, and work out what it does etc, but I've never tried to do anything like this before.

I'm afraid I don't know which compiler was used originally, though it was definitely written in C, and the executable is running on windows.

Can anyone give me some pointers?

Thanks.

Try this or another disassembler and hope it works - there's no sure thing for this.

You can only dissasemble to assembly code reliably....

Better to rewrite what you need if you dont have the original code