In computer science a registry generally stores information and allows other entities to retrieve it later (so it's not evil and not invented by Microsoft ;-). Registries are often used in different variations in distributed systems like e.g. CORBA or Jini to provide knowledge about the whole system (e.g. all available objects or servers) to each member of the system.
Registries normally only contain information which has previously been 'registered' into them (therefore the name) and don't discover or deduce information on their own, which distinguishes them from network monitors, databases and expert systems.