Title: Create temp file
Use for solving of this problem GetTempFileName function.
procedure TForm1.Button1Click(Sender: TObject);
var
St1, St2, St3: array[0..MAX_PATH-1] of Char;
begin
St1:='c:\temp';
St2:='sss';
GetTempFileName(St1, St2, 0, St3);
end;