Ok, so I'm new but I have definitely shifted through this site before for mac help but this time I could not find a thread that fit my problem. My account is under Natalie ___ (last name) which is the only account on the computer, which I ASSUME is the administrator account. Anyways, whenever I try to install anything, it asks for an "administrator username and password". So I type in Natalie ____ and then my password and it says "This is an invalid username or password. Try again". I don't understand why I'm not the administrator because it's a macbook 10.5.1 and I'm the only one that uses it. So, then I try to change my password by putting in the Max OS disk, holding down on C, resetting my password, and this thing comes up that says "System Administrator (root)" and "Natalie _____". So I was like okay...weird. So I reset Natalie ____'s password AND the system administrator to the same thing and then reset, ejected the disk blah blah blah. So I try to log on again and poof doesn't let me. So I try "System Administrator (root)" same password, still invalid. So what I'm asking is...WHAT AM I DOING WRONG!?