Are you unable to login as ‘admin’ on your router? Do you have Norton Internet Security installed on your PC?
If you are using Norton Internet Security, then it can prevent you from logging in on the admin account when trying to access your router’s settings. The solution is to temporarily disable Norton Internet Security when you want to login as admin.
Also be aware that you should use Internet Explorer (not Firefox, Opera etc) when accessing the router, as that is the most reliable approach.