需要用到的一个函数：

LONG SetWindowLong(

  HWND hWnd,

  int nIndex,

  LONG dwNewLong
);

program Project;

uses
Forms, Windows,
 ufrmMain in 'ufrmMain.pas' {frmMain};

{$R *.res}

begin
Application.Initialize;
SetWindowLong(Application.Handle,GWL_EXSTYLE,WS_EX_TOOLWINDOW);

Application.CreateForm(TfrmMain, frmMain);

Application.Run;
end.

http://blog.csdn.net/yanjiaye520/article/details/6659516