>>>Maybe I lead you into confusion, Tore. You said "if you want to replace the running program", and I clarified that I never wanted to do that, because I know it cannot be done. I want to replace a program that calls another, not a program that is running. The caller is the main program, it's the callee that will perform the replacement.
>>>
>>>I thank you for all your remarks.
>>
>>So to use my earlier terms, you want the "main" program to replace the "loader"?
>
>Antonio wants to launch Updater from the main program and quit the main program. The Updater will replace the main program and start it again.

OK. Wouldn't this pseudocode work:

*Main.exe
Shellexecute Updater
quit

*Updater
Do killMain && Sergey's code to make sure that Main.exe is removed from memory
Copy file newmain.exe to main.exe
Shellexecute Main
quit