Title: Prevent window from resizing
You should trap WM_GETMINMAXINFO message. In your form's class declaration put this:
procedure WMGetMinMaxInfo(var Msg: TWMGetMinMaxInfo);
message WM_GETMINMAXINFO;
and in the implementation section:
procedure TYourForm.WMGetMinMaxInfo(var Msg: TWMGetMinMaxInfo);
begin
inherited;
with Msg.MinMaxInfo^ do
begin
ptMinTrackSize.Y:=200;
ptMaxTrackSize.Y:=400;
end;
end;