This may help, any way check it out!!!!
Recently I changed my AntiVirus from PC-Illin Suite (Expired) to Avast,
prior to which I had a network working sharing Internet, files, printer, etc.
After installing Avast I lost my home network and it was due the fact that
Avast has a module called P2P Shield & Network Shield and I had to disable to
the P2P Shield, then everything was back to normal.
Other AV programs have Network Protection modules, you need to ensure these
are set up th allow your home network traffic to flow.
This is assuming that all other network settings are set correctly, such as
permissions, printer sharing, etc.
If you require assistance to set up the network more info is required -
What type of connection, LAN or wireless?
Are the drivers up to date for the router/ printer?
Which computer is the printer on XP or Vista?
Make sure you follow directions for setting up the network correctly
There are other posts in this discussion group which will refer you to
details of how to set up a network, check them out!!!!!