Try the followings:

1. If you have forgotten your LinkSys router password, the easiest thing to do is to reset your router to the factory default settings.

To restore the router configuration to factory defaults, hold the reset button on the unit for 30 seconds.

2. Once your router is hard reset, you will need to login and reconfigure it again.

To reconfigure your LinkSys, connect a PC to one of it's Ethernet ports, load a web browser, and go to the URL click here. This will take you to a popup box which asks you to enter a username and password to login to your router.
LinkSys Default Password

On older LinkSys routers, the default username is blank and the default password is "admin." On newer Linksys routers, both the default username and the default password are set to "admin."

Once you are past the login screen, you are able to reconfigure the LinkSys router.
You want to go to the management tab and change the administrator password to something else to keep others from accessing your router.

3. After changing the administrator password then you will need to enable WEP or WAP security so your nosy neighbors aren't tapping into your wireless network. I am picking up 4 networks with my pc antenna.

To access a Thompson router
User is Administrator
Password is left blank

192.168.1.254