>Is there any way they can de-compile my compiled exe from vfp7/8?
Yes, see
www.xitech-europe.co.uk - look for ReFox. If the exe is protected with products like Konxise or Thinstall then ReFox will not work. But even then nothing offers full-proof protection.
In the End, we will remember not the words of our enemies, but the silence of our friends - Martin Luther King, Jr.