We have a Dell E521 with Vista Home Premium in the shop that has 4 users on it. One of which is a Guest account. The other three users are standard account type and the Guest account is set as Guest and Administrator account type. I have tried everything I could think of to try to change the account types to what they should be, but when ever i do it tells me "Access denied." I have booted to Safe Mode and no Admin account. I can't even create another user because no matter what I name the user it tells me that it has invalid characters in the name, when all I was trying to name the new user account was "Test." Any help would be appreciated. P.S. I ahve already scanned all users with MalwareBytes and SuperAntiSpyware so I think its clean.