Not quite clear as to your problem. Are you trying to access the web-based configuration page for the router (for which you need an
administrator password)? Or are you trying to make a wireless connection to the Internet via the router (for which you need the wireless
security key)?
Those are two separate passwords, and you may be able to retrieve them both. The
administrator password would be stored in the computer that was used to configure the router. The
security key should be in the computer which configured the router, as well as any computer which made a wireless connection to the router.
You may find it helpful to check the owner's manual. If you don't have that available, you can download a copy here:
http://en-us-support.belkin.com/app/product/list/q/routers/Be sure to specify the correct router model.
If you can access the web-based configuration page for your router, you should be able to view (or reset) the wireless security key. (Check the owner's manual for your model.)
For many Belkin routers, the URL for that page is simply: http://router
Then select "Security", and following the onscreen guidance.
If you're not able access the router's configuration page, and the passwords are stored, you should still be able to retrieve them by installing some free software.
For the computer that configured the router, download and install this program:
RouterPassView by NirSoft
http://www.nirsoft.net/utils/router_password_recovery.html
http://www.softpedia.com/get/Network-Tools/Misc-Networking-Tools/RouterPassView.shtml
For a laptop that connected to the router, download and install this program:
WirelessKeyView by NirSoft
http://www.nirsoft.net/utils/wireless_key.html
http://www.softpedia.com/get/Security/Decrypting-Decoding/WirelessKeyView.shtml