I was having a problem and so reinstalled a system from the OSX DVD, saving the old one ("Previous Systems" folder was created). New instrall didn't help the problem I was having, so I would like to go back to the old system. How can I make the "Previous Systems" active, or restart with it? Restoring with Time Machine will erase the entire volume, so I do not want to do it. Just start with the Previous Systems. Please help!