how to add BDC into Network.

My network has 4 PDC located in separated department, none of them has BDC attached to it, I am afraid that any of 4 PDCs can be crashed by any reason.I wonder what is the official procedure to add BDC into those PDC without shutting down any server, and what else I need to pay attention to complete the whole process of installation.

Your help is higly appreciated.