When you try to open a non-blueJ JAR file that is on a read-only folder (or
read-only floppy/usb) this is not possible.
1. It should be possible to specify an alternale location for the extracted
2. the error message is now: "The output directory for the archive being
extracted already exists". This is incorrect and should read "the output
directory [name] cannot be created. Make sure you copy the archive to a
writable folder first." or something similar, unless of course the user is
given the option to specify his own location for the extraction.