go online, but not visibile in the network, very strange....

Hello,

I have a very very strange problem. I have 2 computers (XP SP2). One of
them receive the internet (let's say C1) and share to the other computer
from network (C2). Both of them with network ID : WORKGROUP.
From C2, I disabled the firewall. The computer that receive the
internet -C1-, has 2 ethernet cards, so with an automatically obtained IP,
and with an internal IP : 192.168.0.1. C2, has a fixed IP 192.168.0.2 but
with 192.168.0.1 as gateway.
The problem:
C2 can go online, so browse the internet, downloads staff, etc...
(actually this post is I made from C2), but cannot see C1's shares and
reverse. So in conclusion C1 is not visible to C2 and C2 is not visible to
C1, only when i ping from C1 to C2 and vice-versa.

There is somebody with an idea?

Thank you a lot in advance!

Best regards,

Alex