operastarlet,
I'm not sure if this will help, however I think the reason that you saw your mac data and not your PC's is probably because you had the same short names for both machines and your mac was probalby running windows sharing. This will cause your Mac to share its folders using that SMB shortname. In the windows world ie: Server Message Blocks, it is not a good idea to have two machines on the same network with the same name. I would make sure that the machines have different names. I have always been successful connecting from a MAC (OS X 10.2 or higher anyway, since I didn't really do this with earlier versions) using SMB://ipaddress/sharename so for Example SMB://192.168.4.1/c$.
Run some simple tests first. Make sure that you can ping the IP address of the PC successfully before attempting to connect. If you can not ping that machine, then you will not be able to connect to it. You can ping it either from a terminal ex) ping 192.168.4.1 or using the Network Utility which is found in your /applications/utilities directory.
[Edit] Another test that you can run, once you can ping the IP address of the PC, is to use the Network Utility and run a port scan on the IP address of the PC. You should see the PC listening on port 139 NetBIOS-ssn. If the PC is not listening on this port, then there may be issues with its server service. As was mentioned before the PC will need to be running NetBIOS over TCP/IP for the Mac to connect to it. The PC and Mac will first start to talk on port 139 to negotiate a TCP high port to continue the NetBIOS session. If the PC is not listening on port 139 this initiation of the NetBIOS session will never occur. If you do not see this you may want to check that the PC is running its File and Print sharing and is running NetBIOS over TCP/IP. [end Edit]
Once you can ping the PC, verify what accounts have access to the share you are trying to mount.
Then try to connect using smb://ipaddress/sharename
When prompted for authentication, I would recommend using the NetBIOS name of the PC as the workgroup, then enter the user name and password.
I hope this helps.
[Edit] BTW if you are only trying to connect from the Mac to the PC, I would turn of PC sharing on the Mac, this does not need to be on to access the PC, and may only be confusing the issue. I would try to make the environment as simple as possible when troubleshooting an issue. [end Edit]