1) Reset the router by holding the reset switch in for ten seconds while the router is powered.
2) Connect a PC to a router switch port.
3) Open a web page to the router's configuration page (see the Router manual).
4) Turn off the Router's DHCP Server.
5) Set the Router's IP address to static, and write the IP address and Netmask down, so you'll know it next time you need to access the router.
6) Reboot the router.
You now have a switch. DHCP is turned OFF, so it won't interfere with your network. IP addresses for wireless clients will be offered by your networks DHCP server, NOT by the Netgear router. Turn the wireless section OFF if you aren't going to use it.
You can always talk to the router by hooking up a PC that has a STATIC IP address set to the same subnet range as the Router's.
Example: Set the Router to address: 192.168.2.1/255.255.255.0
Set the PC to address: 182.168.2.2/255.255.255.0
They'll be able to talk and you can change the Router's settings if necessary.