Just a quick question; I just received a SL upgrade DVD for one of my Macs, in the post, and it had the disc number: "2Z691-6557-A". I was a bit surprised that the DVD just came in a simple paper sleeve, tossed into a padded envelope with 2nd class postage. Is this the experience of others?. Also, is this particular upgrade DVD (with the same disc number as mine) capable of erase and install?. I don't like doing upgrades, I'd rather start fresh. Also, I'm currently doing an MD5 checksum on my DVD; I shall report back with the hash value, if some of you wouldn't mind comparing it with your hash value from the same DVD and also from the full retail & box set DVD. Thanks. MD5 of 27691-6557-A: Code: e4240ff044a569765dd3db3469a881c5 PS: I don't understand why the disc number is DIFFERENT, on the inside of the spindle hole: 2Z693-7059-A (underneath - see attached macro).