Also make sure you have the appropriate accounts specified as sysadmin fixed server role members before dropping BUILTIN\Administrators. Last thing you want to do is drop that group and then realize you don't have access back into SQL Server.
K. Brian Kelley
http://www.truthsolutions.com/
Author: Start to Finish Guide to SQL Server Performance Monitoring
http://www.netimpress.com/shop/product.asp?ProductID=NI-SQL1
K. Brian Kelley
@kbriankelley