As you mention its a RX---- that means to me a itanium architecture which I am not familiar with ( only had one box and wasnt me that did the install...) I have no idea how the licensing works in...
Your only chances are either ask HP, or find someone with the CD / DVD ... You can install HP-UX 11iv3... Now thats ages I havent been looking at how were done the CD for 11i after v1 but till then...