Hi,
As well as all the correct ptotcols etc.
Have you set all the hard disks on each machine to shared and enabled file and print sharing on each machine.
My computer select each HD and right click
Each machine also needs to have the same Workgroup name and have unique names on your network.
If you are running a Firewall each machine also needs to have the other machines as trusted sites / zones / IP addresses.
I would not recommend runing without a Firewall or AV for that matter.
You may get Internet Access from each machine without this but you will not get a network up and running.
If you have not been running a Firewall & AV & Spyware removal software then you need to install these and update them all.
hth
Ceri