It would have helped if you would have listed your PC Model Number and Operating System and how you are connecting to the DSL modem - via the Ethernet RJ45 cable or via USB.

But, that error, when doing a Google search is a "Dial Up" error.  Do you still have the "Dial Up Network Connection" listed and are you trying to "dial" with the DSL? 

When you power on the PC and Windows starts you should be automatically connected to the network (this assumes you leave the DSL modem powered on and it is in sync before you power up the PC).  However, in order for Internet Explorer to access the "LAN" network you must delete any dial up connections listed in the Internet Options - Connections Tab.  If you still have the Dial up connection listed it will never try to access the Internet via the DSL connection.

If you are unsure what to do, it's going to cost you but the best thing is to have a local computer tech come out and get you going.  The phone company isn't really going to help you as it's the customers responsibility to configure their PC. 

It's also hard to "lead someone by the hand" and get them going with a forum like this.