SelectDirectory在某些计算机上不包括驱动器

解决方法
请TFileOpenDialog改用*。
放FileOpenDialog1.Options:= [fdoPickFolders,fdoPathMustExist]

现在，您将看到一个对话框：

• 一直有效。
• 允许复制粘贴

*）不要与TOpenDialog混淆，后者不允许您仅选择文件夹。

Solution for Windows XP
Note that the new TFileOpenDialog only works for Vista and above.
Your program will not work on XP if you include this control.
If you start the dialog on XP it will generate an EPlatformVersionException.

You may want to use the following code instead if you want to be backward compatible:

uses JclSysInfo; //because you have XE use JCL.

...
var
  WinMajorVer: Integer;
  Directory: string;
  FileDialog: TFileOpenDialog;
begin
  WinMajorVer:= GetWindowsMajorVersionNumber;
  if WinMajorVer < 6 then begin //pre-vista
    //To show the root Desktop namespace, you should be setting the Root parameter to an empty string ('') instead of 'Desktop'
    FileCtrl.SelectDirectory('Caption', '', Directory, [sdNewUI, sdShowEdit]);
  end else begin
    FileDialog:= TFileOpenDialog.Create(self);
    try
      FileDialog.Options:= [fdoPickFolders,fdoPathMustExist];
      if FileDialog.Execute then Directory:= FileOpenDialog1.FileName;
    finally
      FileDialog.Free;
    end;
  end;
  Result:= Directory;
end;

Recommended reading:
detect windows version

EDIT

FileCtrl.SelectDirectory('Caption', 'Desktop', Directory, [sdNewUI, sdShowEdit]);

The 'Desktop' goes into the Root parameter, which is handled like so:

...
    SHGetDesktopFolder(IDesktopFolder);
    IDesktopFolder.ParseDisplayName(Application.Handle, nil,
      Root, Eaten, RootItemIDList, Flags);
...

Here's what MSDN for IDesktopFolder.ParseDisplayName has to say:

pszDisplayName [in]
Type: LPWSTR
A null-terminated Unicode string with the display name. Because each Shell folder defines its own parsing syntax, the form this string can take may vary. The desktop folder, for instance, accepts paths such as "C:\My Docs\My File.txt". It also will accept references to items in the namespace that have a GUID associated with them using the "::{GUID}" syntax.

Note that the documentation states that the desktop folder will accept paths and guids. It does not accept 'Desktop'. Because that's neither.

The fact that 'Desktop' as a root works on one system but not another is some undocumented fix made in an older/newer version of the IDesktopFolder interface.

技术解决方案
使用''的是在我上面的代码所示的“根”。

显然，这SelectDirectory是Microsoft的一个非常糟糕的设计，永远不应该使用。它只是在很多方面都糟透了。我建议尽可能不要使用它。