AirPort Extreme fails to connect to internet:
I have an iMac 2.16 GHz Intel Core 2 OS X 10.4.11 equipped with Airport Extreme (ox14E4, ox87) seeking wireless connection to a Netgear Wireless-G Router (WGR614v9), which is in turn connected to a cable modem from Time Warner Cable. The wireless connection has operated well for over 6 years, but has become increasingly spotty and unreliable. Recently, the wireless connection has failed to this computer completely, though wireless connection works fine to a PC-DOS laptop nearby, several iPhones, and a newer iMac elsewhere within range. The Internet Connect window indicates that AirPort is On, and Signal Strength is often (but not always) High. It also indicates that AirPort has intermittently connected to and recognized my Netgear router. But every attempt to open Safari results in a 'not connected to the internet' message, and no amount of scanning in the Network Preferences pane rarely finds the Netgear connection. When I try to open the Netgear connection as a new connection, I repeatedly get a 'connection failed, try again' message.
I am a relative newby to computer troubleshooting, and without any internet connection to the problem computer, I have no way to download any old or new software or firmware, or make use of any online links to fixes. Can anyone guide me through a NON-INTERNET-BASED means of resetting my AirPort Extreme, or of re-establishing the necessary internal computer settings to reacquire a wireless connection?
Or am I limited to carting my iMac to the nearest Apple genius bar for troubleshooting and repair?
iMac, Mac OS X (10.4.11)