procedure FindFiles(StartFolder, Mask: string; List: TStringList;
    ScanSubFolders: Boolean = True);
var
    SearchRec: TSearchRec;
    FindResult: Integer;
begin
    List.BeginUpdate;
    try
      StartFolder := IncludeTrailingBackslash(StartFolder);
      FindResult := FindFirst(StartFolder + '*.*', faAnyFile, SearchRec);
      try
        while FindResult = 0 do
          with SearchRec do
          begin
            if (Attr and faDirectory) <> 0 then
            begin
              if ScanSubFolders and (Name <> '.') and (Name <> '..') then
                FindFiles(StartFolder + Name, Mask, List, ScanSubFolders);
            end
            else
            begin
              if MatchesMask(Name, Mask) then
                List.Add(StartFolder + Name);
            end;
            FindResult := FindNext(SearchRec);
          end;
      finally
        FindClose(SearchRec);
      end;
    finally
      List.EndUpdate;
    end;
end;

procedure TForm1.Button2Click(Sender: TObject);
var strs: TStringList;
      i: integer;
begin
    strs:=TStringList.Create;
    FindFiles('C:\','*.jpg',strs,False);
    for i:=0 to strs.Count-1 do
      Memo1.Lines.Add(strs[i]);
end;