Had a funny problem at work to do with clustering, we're not entirely sure if there was a problem with the cluster because we removed Builtin\Administrators. I was the third person brought in to resolve this problem so I'm not quite sure what fixed it. I find clustering kinda scary but also really interesting. Anyways, two links if you're interested
SQL Server 2000 Failover Clustering
http://www.microsoft.com/technet/prodtechnol/sql/2000/maintain/failclus.mspx
SQL Server 2005 Failover Clustering White Paper ( for download )
http://www.microsoft.com/downloads/details.aspx?FamilyID=818234dc-a17b-4f09-b282-c6830fead499&DisplayLang=en
The problem we had was related to this...
BUG: IsAlive check does not run under the context of the BUILTIN\Administrators account in SQL Server 2000 Enterprise Edition
http://support.microsoft.com/?id=291255