I have a RCA dcm 305 cable modem
Realtek RTL8139 Family PCI Fast ethernet NIC (built into the motherboard)
I am using Mediacom High speed Internet
the ISP told me that the modem had an assigned MAC, and they use DHCP

I am trying to get my internet working on madrake 9.1, but no luck so far, I have used the internet connection wizard, but I haven't had any luck yet. Any idea what I should do, or links to websights with help would be great.

Make sure you have this in /etc/modules.conf
alias eth0 8139too

The cable modem is your gateway so you need it's internal IP. I guess they were saying they would give the IP to the cable modem via DHCP. So you need to configure your NIC on the same network as the cable modem.

You should have a file /etc/sysconfig/network that looks something like this:
$ cat /etc/sysconfig/network
HOSTNAME=spongebob
NETWORKING=yes
GATEWAY=192.168.0.1
GATEWAYDEV=eth0

The GATEWAY IP may be different and use your own hostname.

Also to configure the NIC you need a file /etc/sysconfig/network-scripts/ifcfg-eth0 that looks something like this:
cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=static
IPADDR=192.168.0.2
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
ONBOOT=yes

Of course the IP's all depend on the cable modem internal IP. If for example the cable modem has an internal IP of 10.10.0.1 then your file would look like this:
IPADDR=10.10.0.2
NETMASK=255.255.255.0
NETWORK=10.10.0.0
BROADCAST=10.10.0.255

<edit> If you change anything and you want to test it just do this:
service network restart