Local Windows administrators should not also be SQL database administrators. These roles are very different and are typically performed by different people.
Remove BUILTIN\Administrators from the sysadmin role.
Note: There are special circumstances that require Administrators to belong to the Sysadmin role. These circumstances are outlined in the following Microsoft Knowledge Base articles:
SQL
Server Agent Does Not Start and Displays Error 18456 (Q237604)
How to
Prevent Windows NT Administrators from Administering a Clustered SQL Server (Q263712)
IsAlive Check Does Not Run Under the Context of the BUILTIN\Administrators
Account (Q291255)
Microsoft Search Service May Cause 100% CPU Usage if BUILTIN\Administrators
Login is Removed (Q295034)
Important: If you are running Small Business Server and remove all local administrators you will no longer be able to manage your SQL server locally.
Microsoft SQL Server 2000 Security
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