[Raistlin]

You shouldn't need to specify a MAC address in the router.

Your Cable Modem will attach itself to the MAC of the router, it really shouldn't care what MAC address you have setup on your PC.

You shouldn't need an IP address set up on your PC, it should automatically be assigned one by the router.
Right click on the network adaptor icon (Start > Control Panel > Network Connections in XP) and select the General Tab. Highlight TCP/IP and click the Properties button.

This should be set to "Obtain an IP Address Automatically".

Now close all of that and go back to the network connections box.

Right click on the network icon for your connection, select Disable and let it do its stuff. When that is done, right click on it again and select Enable.

Now right click on it again and select Status.

Click on the support tab and post back the first two blocks of numbers from the IP address. Mine are 192.168.