sysadmin

Members of the sysadmin fixed server role can perform any activity in the server. By default, all members of the Windows BUILTIN\Administrators group, the local administrator's group, are members of the sysadmin fixed server role.

Server-Level Roles

Permissions of Fixed Server Roles

sp_helpsrvrole (Transact-SQL)
sp_helpsrvrolemember (Transact-SQL)
sp_srvrolepermission (Transact-SQL)
Security Considerations for Databases and Database Applications

Getting SQL Server 2005 Assistance