|What is the model number of your actiontec modem?|
I suspect it's a combo unit.......which is to say, it's a combination modem, router, and wireless access point.
If it is a combo unit, then you'd need to do a port forward on it, and then another on your second router. The port forward on the actiontec would point at your second router. The forward on the second router would point at the computer you wish to connect to.
When in doubt, read the manuals.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.