In addition to the previous reply (which mostly relies on an external link that may disappear in the future, rendering the answer useless for others with the same problem), it is implicit that using these methods to reset the password to factory default will reset all of the router's configuration to factory defaults as well.
If you are unable to access the settings to use its menu option to erase the configurations, because you don't know the current password, you'll need to use the reset button. On Netgears of that vintage, the reset buttons were recessed under the back panel, with a red circle indicating their locations. e.g.
Use a plastic scribe, toothpick or straightened paperclip to hold the reset button depressed for at least 5 seconds while the router is powered on. Since you can't see it, there is tactile feedback when the button is depressed (50/1000ths of an inch or so).
After about 5 seconds, the power LED should change colors (typically from solid green to blinking yellow). Release the button and the router will reboot (the power LED will turn solid green again).
Once the reset is complete, you should be able to access the settings when connected directly to one of its LAN ports by using a browser to surf to the IPv4 address 192.168.1.1, then logging into the popup dialog with the User name admin and the Password password.
N.B. the words "admin" and "password" (without the quotes) should be in *bold* but fixya's online editor appears to be defective.