I recently bought a used MacBook. I rebooted with the Install disks (10.5.2). I'd like to move to Lion, so I 1st tried to update to the latest Snow Leopard. I clicked on the Apple icon > Software Update. It gave me 4 packages to update, including OS X (10.5.8). I clicked on Install, etc. It ultimately gave me an error: "The update 'Mac OS X Update Combined' can't be saved. You do not have appropriate access privileges. The Installer package has been moved to the Trash. To try again, open the package from the Finder." 1st, I only have 1 user account, and it has Admin privileges. What more do I need? 2nd, Trash is empty. The Installer package wasn't there. 3rd, after all this OS stuff is sorted out, I plan to securely erase the disk free space. Is there anything else that I should do? Is there any information about the previous owner that needs to be replaced?