From the manual:
There are two ways to reset the router's factory defaults:
1) Use the Factory Defaults function on System Tools -> Factory Defaults page
in the router's Web-based Utility.
2) Use the Factory Default Reset button: First, turn off the router's power. Second,
press and hold the default reset button then turn on the router's power, until the
SYS LED lights up (about 3 seconds). Last, release the reset button and wait
for the router to reboot.
*Edit*
Just so you know, the manual referenced 192.168.1.x. Yep, 192.168.1.1 is the default ip for the router, try 192.168.1.2 or above.