Is it necessary to configure MSDTC as a clustered resource for SQL Server clustering to work?
No. MSDTC is required only if you need the ability to perform distributed transactions on your cluster. If you intend to use linked servers or perform replication (snapshot/transactional with immediate/queued updating subscribers), MSDTC is required. For more information, see “Distributed Transactions architecture” in SQL Server 2000 Books Online.