I couldn't find anything on activetek...
If it is a modem, it should have an rj-45 port on the back. If you had only one machine you could connect it directly to that port. If you have more than one, you need a router. The router ties all the machines together into one network and if an address is not on the local network, it sends the packets out its wan port - to which is connected the modem.
So...if the activetek is really a modem, you connect it to the Belkin router's wan port and you connect all the other machines to the Belkin's lan ports. The Belkin router should be configured to use DHCP, which it sounds like it already is if your 'basement' machine used to be connected to it and was assigned an IP of 192.168.1.2.
How many machines do you have (basement, roku, more?) and how were they previously connecte? Fios modem or not, for internet access you had to have the Belkin router connected to some other kind of modem, whether cable or DSL.
Pictures of the back of the activetek would help.