How to create setup disks

We are having 3 NT4.0 servers in our network. Now i want to create setup disk. whenever i am trying to execute the followoing commain winnt/ox it’s trying for fresh installtion and telling cannot install,use winnt32.exe. how can i create setup disk.is there is any other way? should i create separate setup disks for all 3 NT servers or i can keep one set. Pls. give solution.