For WRT300N router try upgrading the firmware of the router & keep on holding tightly the reset button in such a way that power light is blinking on the router & then do a complete network power cycle i.e., unplug the power cables from the modem & from the router & then plug in the power cable to the modem first once all the lights are solid green you could plug in the power cable to the router & check out it will definately work!!
Open the setup page of router using 192.168.1.1 then put in the password as admin...all you need to do is do the wireless settings such as Radio Band Frequency to Standard 20 MHZ frequency,channel to 11.
Also,the advanced wireless settings to Beacon Interval=50,Frag thres=2306 & Rts thres=2307 & then uncheck a Block Anonymous Internet Requests & it will definately work!!!