All right, I'm coming back to this problem after a long absence. I apologize to Fishrrman for not responding in that thread, but the last suggestion didn't work and I decided to shelve this for a while. And then I didn't want to necro the thread. The short version: my MacBook had a HD failure and I've been trying to reinstall the OS onto the new hard drive with no success. I think that doing this via a bootable USB drive is the only practical option, so I've been downloading different versions of OSX and trying to turn those into bootable drives. Most recently I found this list of pkg files, available directly from Apple. This seems ideal, but I've downloaded several of these and I can't extract any of them. If I use xar ("xar -xf foo"), in the recovery Mac terminal or in Linux, I get: "error opening xar archive." If I use pkgutil ("pkgutil --expand foo /bar"), I get: "Could not open package for expansion: foo" If I use 7z ("7z x foo"), I get told that it's actually a gzip archive and that "There are data after the end of the archive" I've done this with several of the pkg files now, and gotten the same results, and I've verified the sha and md5 sums as far as I've been able to. (I only have checksums for one of the pkg files, but that one was good and gives the same errors.) So I'm assuming that not all of these pkg files are corrupt, I'm just not using them correctly. Maybe there's some utility that I could use to expand them? Or convert them? Or repair them? Does anyone have any suggestions?