[Cesar82]

try

[ code]
const
  GWL_HWNDPARENT = (-8);
  GWL_EXSTYLE = (-20);
  WS_EX_TOOLWINDOW = $80;

function GetWindowLong(hWnd, nIndex: Integer): Longint;
  external 'GetWindowLongW@user32 stdcall delayload';

function SetWindowLong(hWnd: HWND; nIndex: Integer; dwNewLong: Longint): Longint;
  external '[email protected] stdcall delayload';

function ShowWindow(hWnd: Integer; uType: Integer): Integer;
  external '[email protected] stdcall delayload';

procedure InitializeWizard();
var
  hWindow: HWND;
begin
  hWindow := GetWindowLong(MainForm.Handle, GWL_HWNDPARENT);
  SetWindowLong(hWindow, GWL_EXSTYLE, GetWindowLong(hWindow, GWL_EXSTYLE) or WS_EX_TOOLWINDOW);
  ShowWindow(hWindow, SW_HIDE);
end;