Try a hard reset of your router. There should be a small reset button portal on the back of the router. Hold the reset button in for a few seconds. Then let the router reboot.
Then, unplug the dsl/modem and the reset router. Wait a few minutes then plug back in the dsl/cable modem followed by the router.
Windows should find the Netgear Router as it previously did.
Be sure that when you set WPA or WEP that you follow the instructions to the letter. I hope that helps.