public static Icon CreateIcon(string s) 
{
    Bitmap bmp = new Bitmap(16, 16); 
    SolidBrush brush = new SolidBrush(Color.Black);

    Graphics g = Graphics.FromImage(bmp); 
    g.DrawString(s, new Font("Arial", 10f), brush, 0, 0); 
    g.Dispose();
    IntPtr hIcon = bmp.GetHicon();
    return Icon.FromHandle(hIcon); 
}

Function CreateIcon(string s) As Icon
    Dim bmp As New Bitmap(16, 16)
    Dim brush As New SolidBrush(Color.Black)   

    Dim g As Graphics = Graphics.FromImage(bmp)
    g.DrawString(s, New Font("Arial", 10f), brush, 0, 0)
    g.Dispose()
    
    Dim hIcon As IntPtr = bmp.GetHicon()
    Return Icon.FromHandle(hIcon)
End Function

Function CreateIconFromBitmap(Bitmap: TBitmap; TransparentColor: TColor): TIcon;
begin 
  with TImageList.CreateSize(Bitmap.Width, Bitmap.Height) do 
  begin 
    try 
      AllocBy := 1; 
      AddMasked(Bitmap, TransparentColor);
      Result := TIcon.Create; 
      try 
        GetIcon(0, Result); 
      except 
        Result.Free; 
        raise; 
      end; 
    finally 
      Free; 
    end; 
  end; 
end;

Function CreateStrIcon(s : String): TIcon;
Var TmpBmp : TBitmap;
    aRect : TRect;
Begin
  TmpBmp := TBitmap.Create;
   With TmpBmp do
  Try
    PixelFormat := pf8bit;
    Width := 16;
    Height := 16;
    aRect := Rect(0,0,Width,Height);
    Canvas.Brush.Color := clFuchsia;
    Canvas.FillRect(aRect);
    Canvas.Font.Name := 'Comic sans MS';
    Canvas.Font.Size := 8;
    Canvas.Font.Style := [fsBold];
    Canvas.Font.Color := clRed;
    DrawText(Canvas.Handle, PChar(S), -1, aRect, DT_CENTER or DT_WordBreak);
    Result := CreateIconFromBitmap(TmpBmp, clFuchsia);
  Finally
  TmpBmp.Free;
  End;
End;
Utilisation :
 
 Application.MainForm.Icon :=  CreateStrIcon('Cr');