Selecting a directory with TOpenDialog

You can use the TFileOpenDialog (on Vista+):

with TFileOpenDialog.Create(nil) do
  try
    Options := [fdoPickFolders];
    if Execute then
      ShowMessage(FileName);
  finally
    Free;
  end;

Personally, I always use the TFileOpenDialog on Vista+ and fallback using the SelectDirectory (the good one!) on XP, like this:

if Win32MajorVersion >= 6 then
  with TFileOpenDialog.Create(nil) do
    try
      Title := 'Select Directory';
      Options := [fdoPickFolders, fdoPathMustExist, fdoForceFileSystem]; // YMMV
      OkButtonLabel := 'Select';
      DefaultFolder := FDir;
      FileName := FDir;
      if Execute then
        ShowMessage(FileName);
    finally
      Free;
    end
else
  if SelectDirectory('Select Directory', ExtractFileDrive(FDir), FDir,
             [sdNewUI, sdNewFolder]) then
    ShowMessage(FDir)

You do know that the two overloaded functions called FileCtrl.SelectDirectory produce entirely different dialogs, right?

SelectDirectory(s, [], 0);

SelectDirectory('Select a directory', s, s, []);

Just include

FileCtrl.pas

var
  sDir:String;
begin
  SelectDirectory('Your caption','',sDir);
end;

Just leave second argument empty if want to see all directories including desktop. If you set second argument to any valid Path, then your dialog will have that path to top folder and you can not navigate beyond that.

For example:

SelectDirectory('Your caption','C:\',sDir) will not let you select anything beyond C:\, like D:\ or E:\ etc.

So it is good to leave it empty.