[Lord Nikon]

1) Unplug power from the modem
2) Shut the PC down
3) Plug the Ethernet cable in, this should be a straight through cable and not a crossover
4) plug the modem in, wait for the SYN and RDY lights on the front of the modem to stop flashing
5) Turn the PC back on, let it finish booting,

If you don't manage to get online this way, then check the following on the PC

i) In Device manager are there any marks (red or yellow) listed? if so, what are they next to?
ii) In network connections, make sure the IP and DNS for the ethernet card are both on auto detect

If all else fails, open a command prompt (I will assume you are using XP with at least service pack 2 installed, or Vista)
type in the following commands

netsh int reset all
netsh winsock reset