Bell Sympatico Wireless Home Networking

I am using the Wireless Home Networking modem offered by Bell Sympatico (it is a Siemens SpeedStream 6300 for non Bell users). This modem has five ethernet ports on the back (one of which can be selected as WAN or LAN), a USB port and a game console serial port. The modem is also a wireless router.

Before I start with my question the first thing to know is that I am NOT using the wireless features yet. I am using the WIRED ethernet ports on the back.

I have a PC and a Mac (AIO G3) - both are able to connect to the Internet through the modem no problem - but they are not able to see each other on the network. I have networked PC's and Mac's before and it is usually very simple and this is making me crazy.

Is it a modem issue (the user guide says "SHARE FILES THROUGH A HOME NETWORK")? Is it because it does not support Mac (even though I am able to connect to the Internet Bell tells me it can't)? Do I require an extra router connected to the modem (which is also a router) in order to share files?

Any experience getting this modem to work this way would be greatly appreciated.

Tech Info:
Mac AIO G3 w/ OS X 10.2.8
PC w/ Windows XP Home SP1

Thanks in advance.

After about an hour of fiddling with the XP firewall settings last night I realized what I did wrong.

The Mac was connecting to the Internet through PPPoE using the Bell Sympatico username and password. All this was doing was connecting one computer to the Internet at a time (without my knowledge because I was running back and forth from room to room) and not actually networking them.

Once I turned off "CONNECT USING PPPoE" the PC showed up in my iTunes list on the Mac (a sure way to see if the network is working) and vice versa.

Connecting to a shared drive on the PC from the Mac was another challenge. The Mac kept finding the modem as the network (default name "mynetwork"). After trying to login to smb://mynetwork/PCNAME/SHAREDNAME numerous times I finally dropped the "mynetwork" part and it worked.