LinkSys Wireless B Router trouble

This is the same router that I have been using for quite some time. I installed it about a year ago and it worked fine up until I downloaded DSL on my desktop. Now, when the internet is plugged into my router and then attached to my modem, it no longer recognizes that I even have internet. If there's something I'm doing wrong, please help. I have tried LinkSys's website for a manual because my desktop cdrom isn't even running the disk that I originally got when I purchased the router. Again, layman's terms please. Thank you