The answer is yes. But if you want to know how I spent a good part of my long week-end, well let me tell you, the result of typing the command (as root) "cp thunderbird2.tar.gz /usr/lib/*" is to have your computer erase both thunderbird2.tar.gz as well as the entire contents of /usr/lib - the directory where all your applications are located. No recovering from that error; I had to reinstall Ubuntu. It takes very little time to install Ubuntu, true, once you have the disc. Longer to put your computer back the way it was (once again, let me take this opportunity to say back up your data - do it now, if you haven't done it recently - you could be one asterisk away from losing everything).