Is it possible to install antivirus package to the server which in turn protects all the pc's on the domain, this might seem a little far-fetched but then this would reduce the processing power on the client computers (which are part of the domain) and also would help to reduce licensing costs. 

Could there also exist a concept of an antivirus server? amm.. just thinking out loud here, please do correct me if I'm wrong. If such solutions exist I would be highly interested in implementing the same.