Hi, ...schon mal versucht, den ShowModal-Aufruf deiner Login-Form in der Projektdatei noch vor dem deiner Mainform zu starten?
Delphi-Quellcode:
program Project1;
uses
Forms,
Controls,
Unit1 in 'Unit1.pas' {Form1},
Unit2 in 'Unit2.pas' {Form2};
{$R *.res}
begin
Application.Initialize;
Application.CreateForm(TForm1, Form1);
Application.CreateForm(TForm2, Form2); // deine Login-Form
if Form2.ShowModal = mrCancel then Application.Terminate;
Application.Run;
end.