User Accounts in Windows

local user account

Local user accounts allow users to log on and access to resources on the computer that has only local user account was created.
When you create a local user account, Windows XP creates the account only in the computer database security, which is called the Local Security database. Windows XP does not repeat the information a local user account on domain controllers. After a local user account exists, the computer uses a local database on the security authentication local user account, which allows the user to log on to your computer.

Do not create local user accounts on computers running Windows XP that are part of the domain because the domain does not recognize the local user accounts. Therefore, the user can not access resources in the domain and the domain administrator is able to manage the local properties of the account or assign permissions for access to domain resources.

Built-in account:

Windows XP automatically creates an account called built-in accounts. Two commonly used built-in administrator and guest accounts.

Administrator

Use the built-in Administrator account to manage the overall computer and domain configurations, such as creating and modifying user accounts and groups, managing security policies, creating a printer and assign permissions and rights on the account to get access to resources.
If you are an administrator, you should create a user account used to perform non-administrative tasks.

NOTE: You can rename the Administrator account, but you can not delete. As a best practice, you should always rename the built-in Administrator account to provide a greater degree of security. Use a name that does not identify you as the Administrator account, because I do not know which account is.