How do I find the PIN number for my linksys WRT54G2 router

Depending on the type of router, you could have various defaults set, if you never changed them.
You can press the reset button somewhere located on the router itself, using a pen/pin/pencil, and then google your brand of router asking what the default password is.
If it is a Linksys, you could google "Linksys default password" or "Linksys default login" for example.

http://belkashop.com.ua/products_files/WRT54G2_V10_EN.pdf
There.. search for PIN and the first hit helps you how to setup this PIN

When youclick Refresh network list, then Choose yourwireless network and then click Connect to your secured WirelessNetwork, it will asks for a Network Key before allowing you to connectinto your wireless network. This Network Key is either the WEP, orWPA or WPA2 Encryption key that is used to configure the Wireless Router. The Passphraseis an alternate way to setup the Encryption key.
When you are requested for a Network Key, you can just enter the Passphrasethat was used to configure the Encryption key in the wireless router.
For information on securing your wireless network,configuring the wireless router and configuring the wireless card in thelaptop/computer, please click on this link and follow my instructions :- http://www.fixya.com/support/r3559128-wireless_router_security

http://www.columbia.edu/acis/networks/aptnet/linksys/index.html

You should not be asked for a pin.

If its asking for a pin number I would check the sticker on the bottom of the router. it may have the router PIN you are looking for. If not trying typing in your internet browser address bar 192.168.1.1 and find the network settings and see if there is a pin set up, if so write it down or clear it to have no PIN

Two methods to solve your problem:
Method 1:
(1) Using your currently connected and working computers, access the wireless router security page at 192.168.1.1 (page 8 of 44 from the WRT54G2 manual), default password "admin" (page 7 of 44 from the WRT54G2 manual)
PDF file of the Linksys/Cisco Wireless-G Broadband Router User Guide:
http://belkashop.com.ua/products_files/WRT54G2_V10_EN.pdf
You'll need Adobe Acrobat Reader to view/print this file - free from www.adobe.com
(2) get the WEP or WPA password, and enter it into the wireless LAN (WLAN) settings on your 2 additional computers.

Method 2:
Alternatively, access the WEP or WPA key on one of your working PC, by
(1) make sure the printer is working, powered up and online.
(2) invoke "Network Setup Wizard"
(3) wind thru various steps (click-ing NEXT), then select "Print Network Settings"
(4) use the printed WEP or WPA key in the WLAN settings on your additional 2 PCs.

you can get the pin number by contacting the provider.

Yes this is very straight forward

open internet explorer on your computer which is connected to wireless router.

browse to your gateway address. The default for linksys is usually http://192.168.1.1

then it will ask for username and password

linksys default username: (leave this blank)
linksys default password: admin

if that doesn't work try username: admin
password: admin

Once logged into console you should be able to see wireless security settings

Click on that and it will take you through to a page with your security settings on there you will see a wireless key or network key or wireless passphrase.

simply make a note of the key as its written. (If the password is masked or *********** out ) which is the case on some of the newer linksys devices you can simply overtype the password with a new one, bear in mind that you will have to then update any clients that normally connect to the wireless network with the new password. So thats all computers, laptops, DS's Wii's Playstations & Xbox's.

******I'd STRONGLY recommend you DO NOT change the wireless password / security key over wireless you should always do it using an RJ45 ETHERNET cable connected to your computer and the router. *********

Thanks

Pete McDowell
Geek2Door Ltd
http://www.geek2door.com

I have never heard of such. Sound like your computer is tring to get you to enter the WEP key or Passphase to access the router.
If you don't have a WEP key or Passphase setup on the router then you should just be able to click "ok" or "enter" (with the field blank) and bypass this screen.

Also check your network properties on the computer that is giving you trouble. Open your network connection, right click your wireless connection and click on "properties". Check the tabs and make sure you don't have WEP or secure network highlighted in one of the check boxes.