active/active sql server cluster

Hello, Can anyone please explain how the failover processes works on a sql server 2000 2 node active/active cluster.

Given the following
You have 2 node active/active cluster NodeA & NodeB

Question
1. How many SQL instances need to be installed on each node?

2. If the answer to question #1 is one instance per node, then
say if NodeA fails NodeB will take over all the resources of NodeA
including the master database, How does that work , how can once instance (in nodeB) handle two master database i.e its own master database and the one taken over from NodeA.Check this out,

http://www.sql-server-performance.com/clustering_intro1.asp