Is your Belkin wireless? If so then all you have to do is plug the wireless bridge for the Xbox 360 into the back of the 360 console and start trying to search for wireless connections (best to use "Test Xbox Live Connection" for that) and Belkin should come up..
If not then find out certain settings of your Belkin by going on
this link and your user should be admin as well as your password as admin ;) Just get the settings off that page and input them into your console and then it should work if you had any problems with the first method.
All I've heard of the Xbox 360 Wireless bridge is that it is one of those plug and play devices and you dont need to do much to set it up, all positive feedback on the Wireless product. Good luck with your router problem and I hope this helps, if not just look at this page on wireless connections with Xbox Live
here
That should work if everything fails! =]