Как установить разрешение экрана?

Вариант 1:

Author: cpu

Source: Vingrad.ru https://forum.vingrad.ru

ChangeDisplaySettings

Вариант 2:

Author: Зайцев О.В., Владимиров А.М.

Source: https://forum.sources.ru

function SetFullscreenMode:Boolean;
var DeviceMode : TDevMode;
begin
  with DeviceMode do begin
    dmSize:=SizeOf(DeviceMode);
    dmBitsPerPel:=16;
    dmPelsWidth:=640;
    dmPelsHeight:=480;
    dmFields:=DM_BITSPERPEL or DM_PELSWIDTH or DM_PELSHEIGHT;
    result:=False;
    if ChangeDisplaySettings(DeviceMode,CDS_TEST or CDS_FULLSCREEN)
      <> DISP_CHANGE_SUCCESSFUL 
      then Exit;
    Result:=ChangeDisplaySettings(DeviceMode,CDS_FULLSCREEN) = DISP_CHANGE_SUCCESSFUL;
  end;
end;

procedure RestoreDefaultMode;
var T : TDevMode absolute 0;
begin
  ChangeDisplaySettings(T,CDS_FULLSCREEN);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if setFullScreenMode then begin
    sleep(7000);
    RestoreDefaultMode;
  end;
end;

Вариант 3:

Source: DelphiWorld 6.0 https://delphiworld.narod.ru/

procedure ChangeDisplayResolution(x, y: word);
var
  dm: TDEVMODE;
begin
  ZeroMemory(@dm, sizeof(TDEVMODE));
  dm.dmSize := sizeof(TDEVMODE);
  dm.dmPelsWidth := x;
  dm.dmPelsHeight := y;
  dm.dmFields := DM_PELSWIDTH or DM_PELSHEIGHT;
  ChangeDisplaySettings(dm, 0);
end;