delphi判断电脑是否安装了excel

try   
              ExcelApp:=CreateOleObject('Excel.Application');   
              MyWorkBook:=CreateOleobject('Excel.Sheet');   
          except   
              application.Messagebox('无法打开Xls文件，请确认已   经安装EXCEL.','',   
                        mb_OK+mb_IconStop);   
              Exit;   
end; 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

uses Registry;
...

procedure TForm1.Button1Click(Sender: TObject);
var
 Reg:TRegistry;
begin
 Reg:=TRegistry.Create;
 Reg.RootKey:=HKEY_CLASSES_ROOT; 
 if Reg.OpenKey('\Excel.Sheet\CurVer',False) then
   showMessage('Excel 已安裝') 
else
   showMessage('Excel 沒安裝'); 
 Reg.Free;
end;