procedure TForm1.Button4Click(Sender: TObject);   
    var
    sr:TSearchRec;
    Result1, Result2 :word;
    begin
        ChDir('C:\x-hider');
        Result1 := FindFirst ('System.dcu',faAnyFile,sr);
        if result1=0 then
    Begin
        Result1:=FindNext (sr);
    End;
     if result1<>0 then
           begin
              showmessage('asdvxcdra')
           end;

    if Result1=0 then
                  begin
        ChDir('C:\x-hider');
        Result2 := FindFirst ('Windows.dcu',faAnyFile,sr);
        if result2<>0 then
    Begin
        Result2:=FindNext (sr);
    End;
                   end;
     if result2<>0 then
           begin
              showmessage('asdvxcdra')
           end;
    end;

var SR:TSearchRec;
begin
      ChDir('C:\x-hider');
      if FindFirst('System.dcu',faAnyFile,sr)<>0 then
            ShowMessage('aaa');
      if FindFirst('Windows.dcu',faAnyFile,sr)<>0 then
            ShowMessage('aaa');
      FindClose(SR);
end;

function FileExists(const FileName :string) :Boolean;
var
  Code :DWORD;
begin
  Code := GetFileAttributes(PChar(FileName));
  Result := (Code <> DWORD(-1)) and (Code and FILE_ATTRIBUTE_DIRECTORY = 0);
end;

-----------------------------------------------
if FileExists('C:\test.txt') then MessageBox(0,'Файл найден',0,0) else MessageBox(0,'Файл не найден',0,0);