|How are you trying to connect this old router to the network? What are you connecting and to which port on the router? Describe the physical setup.|
What do you mean by "router is not recognized"? What happens, or doesn't happen? What, if any, error messages do you get?
If the router has been configured in the past, it's possible changes have been made to the default settings (ie: LAN IP address). It would probably be a good idea to find the manual (either the one that came with it, or look online at the manufacturer's website) and reset the router to it's factory defaults and then try again.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.