procedure TForm1.StringGrid1DrawCell(Sender: TObject; ACol, ARow: Integer;
  Rect: TRect; State: TGridDrawState);
var i, x, y: Integer;
begin
  if gdFixed in State then exit;
  if ARow <= 1 then exit;
  with sender as TStringGrid do begin
    if aCol < Pred(ColCount) then
      Rect.Right := Rect.Right + GridlineWidth;
    y:= Rect.Top + 2;
    x:= Rect.Left + 2;
    for i:= 1 to aCol-1 do
      x:= x - ColWidths[i] - GridlineWidth;
    Canvas.Brush.Color := clWhite;
    Canvas.Brush.Style := bsSolid;
    Canvas.FillRect(Rect);
    Canvas.TextRect(Rect, x, y, Cells[1,1] );

  end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  stringgrid1.Cells[0,1] := 'Ich bin über alle Spalten in Zeile 2 zu sehen';
  stringgrid1.Cells[0,0] := 'test';
  stringgrid1.Cells[2,2] := 'test 2';
end;

procedure TForm1.StringGrid1DrawCell(Sender: TObject; ACol, ARow: Integer;
  Rect: TRect; State: TGridDrawState);
begin
  with Sender as Tstringgrid do
    begin
      if (arow=1) then
        begin
          //das zu zeichnende Rechteck auf die gesamte Zeile erweitern
          rect:=classes.rect(0,rect.top,GridWidth,rect.Bottom);
          //Hintergrund
          canvas.Brush.Color := fixedcolor;
          canvas.FillRect(rect);
          frame3d(canvas,rect,clBtnHighlight,clBtnShadow,1);
          //text (immer aus Cells [0,1] holen
          canvas.textout(rect.Left+2,rect.top+2,cells[0,1]);
        end;
      //keine weiteren fixierten Zellen selbst zeichnen
      if gdfixed in state then exit;
      //normale zellen
      //Hintergrund
      canvas.FillRect(rect);
      //text
      canvas.textout(rect.Left+2,rect.top+2,cells[aCol,Arow]);
    end;
end;