[Setup]
AppName=My Program
AppVersion=1.5
DefaultDirName={pf}\My Program
OutputDir=userdocs:Inno Setup Examples Output

[Icons]
Name: "{group}\My Program"; Filename: "{app}\MYPROG.EXE"; WorkingDir: "{app}"; Check: InstallIcon;

[Code]
function InstallIcon: Boolean;
begin
  Result := RegKeyExists(HKEY_CURRENT_USER, 'SOFTWARE\Some Path\Some Key');
end;