Hello, Yky, welcome to the Seven Forums.
The username Administrator
is reserved for a built-in administrator account
. If you want to use the name for another account, you need first rename it to "free" the name. Instructions here: Built-in Administrator Account - Change Name
Please keep in your mind that even if you change the name of the user account Acer to Administrator, it's userprofile folder's name remains Acer. Renaming a user account does not change the name of the user folder.
An example: my username is my real first name, Kari, and that's the name I also use for my userprofiles on all of my rigs. If I now decide to change my username on this computer to LarryLaffer, it's OK. Easy and fast done. BUT: it would mean that on this computer, user LarryLaffer's files would be located in folder called C:\Users\Kari, because renaming a user account does not change the name of the folder. Windows user folder name stays always the same it was when the user account in question was created and user logged in first time.