Find all Files in Folder & Subfolders

type
  TStringDynArray = array of string;

var
  Form1: TForm1;
  FileCount: Cardinal = 0;
  Files   : TStringDynArray = nil;
  
//

function FindAllFiles(RootFolder: string; Mask: string = '*.*'; Recurse: Boolean
  = True): TStringDynArray;
var
  wfd          : TWin32FindData;
  hFile        : THandle;
begin
  if AnsiLastChar(RootFolder)^ <> '/' then
    RootFolder := RootFolder + '/';
  if Recurse then
  begin
    hFile := FindFirstFile(PChar(RootFolder + '*.*'), wfd);
    if hFile <> INVALID_HANDLE_VALUE then
    try
      repeat
        if wfd.dwFileAttributes and FILE_ATTRIBUTE_DIRECTORY =
          FILE_ATTRIBUTE_DIRECTORY then
          if (string(wfd.cFileName) <> '.') and (string(wfd.cFileName) <> '..')
            then
            FindAllFiles(RootFolder + wfd.cFileName, Mask, Recurse);
      until FindNextFile(hFile, wfd) = False;
    finally
      windows.FindClose(hFile);
    end;
  end;
  hFile := FindFirstFile(PChar(RootFolder + '*.*'), wfd);
  if hFile <> INVALID_HANDLE_VALUE then
  try
    repeat
      if wfd.dwFileAttributes and FILE_ATTRIBUTE_DIRECTORY <>
        FILE_ATTRIBUTE_DIRECTORY then
      begin
        FileCount := length(Files)+1;
        Setlength(Files, FileCount);
        Files[FileCount - 1] := RootFolder + String(wfd.cFileName);
      end;
    until FindNextFile(hFile, wfd) = False;
  finally
    Windows.FindClose(hFile);
  end;
end;

// Beispiel :
procedure TForm1.Button1Click(Sender: TObject);
var
  i            : Integer;
begin
  Files := nil;
  FindAllFiles('C:\Windows\Temp', '*.*', True);
  for i := 0 to length(Files) - 1 do
  begin
    Listbox1.Items.Add(Files[i]);
  end;
end;