1. Clustering basically requires two nodes.
2. If you have only one system there is no need of going for NT cluster.
3. Cluster work thru the concept of Heart Beat process with Virtual IP address for all clients.
3. For Oracle to work with NT Cluster, you will have to install a separate utility from oracle called Oracle Fail Safe Manager after installing Cluster on Windows NT.

If you still have any doubt on this please contact me at [email protected] or put it on the forum.

thanks,
Srikanth