This question seems to get asked a lot, so I thought I'd post it here. It allows you to make "custom EXE files".
(This code is not a compiler).
You basically have 2 programs, one is your program, the other is one that customizes it. This is the same kind of concept used by installers, self extractors, etc.
It's hard to explain, so it's better if you look at the example projects.
The example is a simple login screen. You write the username/password to the EXE file itself (instead of having to distribute a password file or something with it).
No encryption was used in this example, so if you were to really make something like this then be sure to use encryption.
This is an updated version from one I posted about a year ago.