Problems with guest account set to Admin

Hey, I am really frustrated. I suggested that on my grandmother's computer that there was a user account and an admin account. Ok, fine, but when I got there to update windows and other programs I found out that the Admin account they set up was not a user account but the guest account. I logged into this account to change the user account back to admin from standard so that I could make a new admin user account and delete the guest account. The problem is that I cannot change the user account back to admin, no error it just won't do it. I cannot make a new user account because it gives me an error saying I cannot use the characters ?<>:"{} etc... even though the account is just named Master. I tried unlocking the hidden admin account in command but access was denied. I am at a loss of what to do next. The OS is Win7-64 Home Premium. Also, when I went to update Adobe Air I was unable to because it told me I did not have permission even when I ran it as Admin, could this be related. I was unable to uninstall to do a fresh install of the updated version for the same reason. Any help would be much appreciated.