Changing the machine name

I work on a UNIX HP 10.20 system that recently crashed. I am new with UNIX but I pick things up quick. The system I work on consists of two computers with the same basic hardware config. I have been having trouble loading the program software it uses, NOT the UNIX software, so I used the a recovery tape from one for the other just to make sure I was not having a hardware problem. It works fine but, as we all know both machines now have the same name, not good. Is there a way to change the machine name permently that won't mess everything else up?

set_parms hostname