Microsoft Windows NT Server, Enterprise Edition version 4.0, comes with SP3.
You can install a later service pack, as long as you install it on each node (unless directed otherwise in the Service pack readme).
To install the service pack:
01. Resolve any System event log errors on each node.
02. Create a current ERD and backup.
03. Take all groups offline on one node (Node A) or move them to Node B.
04. Install the service pack on Node A.
05. Restart Node A.
06. Resolve any System event log errors on Node A.
07. Move the Node A groups back from Node B or bring them back online.
08. Take all groups offline on Node B or move them to Node A.
09. Install the service pack on Node B.
10. Restart Node B.
11. Resolve any System event log errors on Node B.
12. Move the Node B groups back from Node A or bring them back online.