Delphi6调用Windows系统外壳进行文件操作时遇到的???

各位同行,现在我把一个Delphi小程序贴出来,
procedure TForm1.Button4Click(Sender: TObject);
var fStruct:TSHFileOpStruct;
begin
  with fStruct do
  begin
     Wnd:=Handle;
     wFunc:=FO_Delete;
     pFrom:=pchar('E:        emp'+#0#0);
     fFlags:=FOF_AllowUndo;
  end;
  try
     if ShFileOperation(fStruct)<>0 then showmessage('Delete Files Error!');
  except
     exit;
  end;
end;
这段代码可以正常执行,但是以下的方式就有问题:
procedure DeleteFileDirectors(aHandle:THandle;sDirectory:String);
var fStruct:TSHFileOpStruct;
begin
  with fStruct do
  begin
     Wnd:=aHandle;
     wFunc:=FO_Delete;
     pFrom:=pchar(sDirectory+#0#0);
     fFlags:=FOF_AllowUndo;
  end;
  try
     if ShFileOperation(fStruct)<>0 then showmessage('Delete Files Error!');
  except
     exit;
  end;
end;
这段代码是放在一个自编的公共函数,过程的单元uPublic.pas.
都有USES ShellAPI,在Form1的单元也有USES uPublic
窗体调用该过程会出错,请问这有什么不当的地方?