I had a cable modem go down and Shaw replaced it with a Nitron modem I have my Linksys extender and I need to reset it with the new passphrase but I cant seem to get inti it

Sure you can if your router has multiple ports (Ethernet). So let say you need a connection in the 2nd level then buy the length of cable and connect teach end to the PC and the modem.
Another option is to buy a WiFi extender.
Here are some samples:
WiFi Range Extenders

If it works sometimes ? when you unplug it then replugging it back in something is wrong with the modem / router or they might need to be reset .
or firmware upgrade
Reset linksy router b> One of the most common fixes for Internet connectivity often involves resetting the source of your Internet connection. If you have a DSL or cable Internet connection, you may use a Linksys router to get on the Internet. When you reset a Linksys router, you'll likely solve your connection problem.

Turn off the power to your computer's modem. Use the switch on your cable or DSL modem to disable it while you reset the Linksys router. Find the reset button your Linksys router. Most Linksys models have the reset option on the back of the router. Use a pointed pen or pencil to press in the reset button on your Linksys router. Hold down the reset button for approximately 30 seconds. Watch the lights on the front of the router. After you reset the router, power will get restored to the Linksys router. Once power's available, you can switch the modem back on. Reconfigure your router. After you reset your router, you'll have to log in and reconfigure your settings. The login name is typically left empty with your password as "admin."
Reset a Linksys Wireless Router b> You may need to reset your Linksys wireless router if you are having Internet connectivity issues or other networking problems. You can reset the router to the default factory settings, such as the default IP (Internet protocol) address, username and password. However, after you perform the factory reset, you can follow the initial setup instructions to replace your previous settings.

Write down any important settings you may have--such as the router's password--before you reset the router. Locate the reset button on the router. Some Linksys models have a reset button on the back side. Other Linksys models have a small pinhole you may need to access by using the tip of a pen or pencil. Press and hold the reset button for a minimum of 30 seconds to perform a factory reset on the Linksys router. The Linksys router should lose power. Power on the Linksys router to initiate the configuration wizard. Reconfigure any previous wireless settings on your Linksys router.

Hope this helps.
b>

* NOTE: If you tried to set-up the WRT-150N Router previously, but failed, with the Router ON, press the "Reset" button on the back panel and hold it down for 10 seconds, then release. This will reset the Router to factory settings and erase all previous data.
then do this :
1. Hook up the Linksys WRT-150N Router to the Modem via a LAN cable.
2. Hook up the Linksys WRT-150N Router to your computer via a LAN cable with the LAN cable in Port #1 on the Linksys WRT-150N Router.
3. Type http://192.168.1.1 in the address bar of your web browser.
4. Log-on to the Linksys WRT-150N Router with these log-on credentials:
Username: linksys (lower-case)
Password: admin (lower-case)
5. Click on the "Clone PC MAC Address" tab.
6. Click the "Clone PC MAC Address" button.
7. Click "Save", click "Continue".
8. Click the "Wireless Security" tab.
9. Choose "WPA2 Personal - TKIP/AES" for encrypted security.
10. Enter encryption password (passphrase).
11. Click "Save", click "Continue".
12. Exit the web browser.
13. Disconnect the LAN cable from the computer and Port #1 on the Linksys WRT-150N Router.
In about 5 seconds, your wireless connection should be up and running.

* NOTE: If you tried to set-up the WRT-160N Router previously, but failed, with the Router ON, press the "Reset" button on the back panel and hold it down for 10 seconds, then release. This will reset the Router to factory settings and erase all previous data.
Then do this
1. Hook up the Linksys WRT-160N Router to the modem(cable, DSL or satelitte)
2. Hook up the Linksys WRT-160N Router to your computer via a LAN cable with the LAN cable in Port #1 on the Linksys WRT-160N Router.
3. Type http://192.168.1.1 in the address bar of your web browser.
4. Log-on to the Linksys WRT-160N Router with these log-on credentials:
Username: linksys (lower-case)
Password: admin (lower-case)
5. Click on the "Clone PC MAC Address" tab.
6. Click the "Clone PC MAC Address" button.
7. Click "Save", click "Continue".
8. Click the "Wireless Security" tab.
9. Choose "WPA2 Personal - TKIP/AES" for encrypted security.
10. Enter encryption password (passphrase).
11. Click "Save", click "Continue".
12. Exit the web browser.
13. Disconnect the LAN cable from the computer and Port #1 on the Linksys WRT-160N Router.
In about 5 seconds, your wireless connection should be up and running.

hi

Configure the Router 1. Step 1
Open your web browser, type " http://192.168.1.1/ " into the address bar and hit "Enter."
2. Step 2
Use "Admin" as the username in the pop-up box and leave the password blank.
3. Step 3
Connect to the Internet and click on "Internet Setup."
4. Step 4
Select your connection type from the drop-down menu. Choose "DHCP" for cable modems or "PPPoE" for most DSL modems. If you are unsure of these options, check with your ISP.
5. Step 5
Set a service set identifier (SSID) to identify the router and change the password.
6. Step 6
Encrypt your wireless connection using a Wireless Encryption Protocol (WEP) key. Under the "Wireless Security" option, enter a passphrase and click "Generate." This will generate a password which will need to be used by any client connecting to your router.

Configure the Router 1. Step 1
Open your web browser, type " http://192.168.1.1/ " into the address bar and hit "Enter."
2. Step 2
Use "Admin" as the username in the pop-up box and leave the password blank.
3. Step 3
Connect to the Internet and click on "Internet Setup."
4. Step 4
Select your connection type from the drop-down menu. Choose "DHCP" for cable modems or "PPPoE" for most DSL modems. If you are unsure of these options, check with your ISP.
5. Step 5
Set a service set identifier (SSID) to identify the router and change the password.
6. Step 6
Encrypt your wireless connection using a Wireless Encryption Protocol (WEP) key. Under the "Wireless Security" option, enter a passphrase and click "Generate." This will generate a password which will need to be used by any client connecting to your router.

there is nothing issue with the linksys ist chk the ipaddress which u had provided to the modem and router is in same serious for eg: if ur modem is in 192.168.1.1 ten provide ur router ip as 192.168.0.1 and also chk whether the connection type is in PPPoE and also chk whether u r able to browse through modem which is provided by the ISP....

Your provider probably sent you either a cable modem or adsl modem. If you connect the single port on the modem to the WAN or Internet Port on the Linksys and then connect the computers to any of the 4 ports that are grouped together, it should work.
Mac or PC, it makes no difference and drivers are not needed.
Unless this is a new router or it is one that you personally configured, I recommend resetting it back to factory default by holding down the little red button for 30 seconds, this eliminates any configuration issues that someone else may have introduced.

Ok, first... hook up your router to your modem. Go and get a drink and chill out for 15 minutes or so... that'll give their network time to realize your MAC Address has changed. If it doesn't work, bring up your browser and type 192.168.1.1 (could be 192.168.0.1 as well) in your Address bar. The default login is usually "admin" (sometimes Linksys leaves the User field blank too) and the default password is "password". Check the status page for a WAN IP Address, if you have one contact Shaw Cable and get them to check to see if they can "ping" it (they'll know what that means). If you don't have an IP Address, you may have to use PPPoE to authenticate your account... verify that with Shaw as well. If it's PPPoE, then you should have a username and password that they have assigned to you. If the first line person can't help you, don't let it go... get them to get a Tier 2 or 3 person on the line.