Try a factory reset. Then connect a computer to the router with an ethernet cable. Don't connect anything else. Reboot the router and the computer. Your computer should get an IP address from the router. If your address is something like 192.168.1.100 your router should be at 192.168.1.1.
If it is still not working, open a command prompt window and enter "ping 192.168.1.1". If this does not get through, check the output of "ipconfig /all". The gateway address of your ethernet card should be the ip address of the router. If it is not 192.168.1.1, try the other address.
Also make sure to turn off any software firewall on the computer.
I was actually wrong, when i ping the 192.168.1.1 it finds it fine. Although when i go to log into the whole linksys menu thing it does not connect no matter one keeps giving me not authorized or whatever... have no idea whats wrong reinstalled and everything still wont let me set up a SSID for the wireless connection
When you connect to http://192.168.1.1/ the username remains empty and the default password is "admin". Again, please make sure to do this when you have connected the computer with a cable to a numbered LAN port of the router and the router is not connected to the internet.
If it still does not work and you have no idea to which password you may have changed it during initial setup you have to do a factory reset: press the reset button for 30 seconds...
No. The password is case sensitive. The default password of the router is "admin" not "ADMIN". For more details look into the user guide, e.g. p.11 for the wrt300n userguide. There is also a screen shot of the popup prompt for the username and password.