Applying SP4 on an active/passive 2 way cluster

I have a 2 way cluster and I want to apply SP4 on it.

Basically, I have 2 servers. Server A runs a default instance and another instance. While the default services is disabled and the other instance is running, Server B runs the default instance and has the other instance disabled. This basically acts like a 2 way cluster (active/passive).

How can I apply SQL Server 2000 SP4 on the 2 servers and have all the nodes come up the correct way? What are the steps to achieve this?Since SQL Server is a shared resource on a clustered server, installing SP4 on one server is automatically done on the other. Everything is transparent to the user/admin.sql