I just bought a 2011 MacBook Air from a friend. When I start it up, it boots to a screen with a eBay icon and a Guest User icon. I can't get to the desktop. The eBay icon is password protected and the Guest user allows me to boot only into Safari to surf the web. How can I get it to boot to the normal start screen? I presume I could do a factory reset but then I would lose the Microsoft Office for Mac that she bought and installed. Any thoughts?