Dimension 4550 Ethernet Card Problem, cannot connect to the internet

I have a dimension 4550 and I just formatted my computer a week ago, but I did not re-install the chipset driver and ethernet controller driver until a few hours ago and now I have problems connecting to the internet. I have checked everything under the device manager thing and the ethernet card seems to be working properly, there's no ! sign next to it. Also, when I unplugged the cable modem from the ethernet slot, it said "network cable unplugged" which means it does detect the network card there. But I just can't seem to connect to the internet. What is the problem here?