Are you using Vista OS in both the computers.
Is the computers are connected to the router
or a switch.
What is the Ip address that you are getting
in both the computers?
Are you able to ping between the computers?
If you are not able to ping between the
Computers, Turn off the firewall and the
Internet security in both the Computers.
Make sure both the computers are in the same
Once you disable the firewall try to share a
file and check you are able to access that
files in other Computer.
If you are able to access the files then try
to share the printer.
Thanks and Regards,