I'd get a Router and use that as your DHCP service to serve up your IP to your system. This will also act as a front line for security to prevent an easy attack as long as you dont open up ports through port forwarding etc and just go with the basic setup and change its default password. Then follow these steps.
1.) Shut everything off, computer, router, and modem.
2.) Turn Modem on and wait about 30 seconds.
3.) Turn router on and wait about 30 seconds.
4.) Turn computer on and upon logging in wait about 20 seconds for your system to pick up an IP from the routers DHCP lease.
5.) Try to get on the internet now, and you should be able to as long s the Modem passed a single IP as it should have from Comcast ISP to the router, and the router gateways that out through its DHCP.
*** Make sure network settings are all set to dynamic including the DNS setting. Your computer will have to connect via Ethernet Cat5 cable to the router and ethernet cable between the modem and the router. If you are currently connected via USB to the modem, do away with that connection means as for it will just be a constant headache and load on your system to translate the USB bus daat packets, which will put a load on your PC.
Cheap router will be around $40 to $70, and cat 5 cables vary in cost on length, but be sure to get Patch Cable and not Cross Over Cables!!!
Good Luck!
