How do I become the "Administrator" of my computer. I bought an Acer laptop from Best Buys in the springtime. It was "pre-setup" by them. Every time I try do something of significance I get a message that, " You are not authorized to make these changes. Contact your administrator". Thank you.
It is not possible to "become" an administrator if you are an ordinary user account. That is actually an important security feature.
What you must have is the password for one of the Administrator accounts that must exist on the computer. There is likely a disabled account called "Administrator" and one new account with membership of the local group Administrators. This password has been set up by the company that installed your computer and if you did not get the password with other documents you should contact them now to retrieve it.