80 GB (750GB Media server )
Macs are just linux you have to pay for
Religion is regarded by the common people as true, by the wise as false, and by the rulers as useful.
You should turn off the DMZ and manual port forwadring, and turn on UPnP if you are using DD-WRT.
The problem probably isn't the router. It's what's ahead of the router. Did your internet service provider give you a "gateway" instead of a modem? If they did, then chances are you have two routers in a row, and that's giving you a closed NAT situation.
You probably have a linksys router. Ask your dad to go to 192.168.1.1 and go to the NAT/QOS tab. Go to upnp and click enable upnp in the "upnp config. box". That should be all that you need to do, unless you have dsl then you might have to take extra steps, but let's try the first option.