Conditionally change application icon with Delphi 2006

I want to produce two different versions of my application, with different icons based on a DEFINE. I succeeded to include different resource files based on the define but I cannot get rid of the MAINICON in the default .res file of my project.

I added a resource Version1.rc file with the following line:

MAINICON icon "resource\icons\Version1.ico"

But if I try to compile MyProject using the IDE I always get the following error:

E2161 Duplicate resource: Type 14 (ICON GROUP), ID MAINICON; File C:\MyProject\Version1.RES resource kept; file C:\MyProject\MyProject.RES resource discarded.

I tried to edit MyProject.res using a resource editor and deleted MAINICON, but delphi automatically seems to recreate the file including the icon.

I found a solution thanks to the comments of David Heffernan. I ended up with the following:

• In the IDE I removed "Include version info" under project options and removed {$R *.res} in the project file.
• I removed the file MyProject.res
• I added a file versioninfo.rc with the information, that I formerly provided in the IDE, as described here.

• I added the files icon_version1.rc and icon_version2.rc, that looked like this:

  LANGUAGE LANG_NEUTRAL, SUBLANG_NEUTRAL
  MAINICON icon "..\resources\icons\version1.ico"
  

• I added a file Resources.pas to my project, that looked like this:

  unit Resources;
  
  interface
  
  implementation
  
  {$IFDEF VERSION1}
      {$R ICON_VERSION1.RES} //from ICON_VERSION1.RC
  {$ELSE}
      {$R ICON_VERSION2.RES} //from ICON_VERSION2.RC
  {$ENDIF}
  
  {$R VERSIONINFO.RES}  //from VERSIONINFO.RC
  
  end.
  

• I modified my existing script compile_resources.bat to compile the additional resource files.

Now if I define VERSION1, my application has the icon icon_version1.ico, otherwise icon_version2.ico. One caveat: If version info (or icon) is modified I have to run compile_resources.bat to reflect the changes.