Upon opening Outlook 2007, I received the following error - "Cannot open file extend.dat." Apparently, one solutioins is to change that file to extend.old. When I tried that fix I received another message that I didn't have the proper administrative authority. I am the Administrator and no one else uses my computer. Why can't I change this folder. BTW, after restarting my computer yet again, the first error message was gone. What gives?