I had a router on this computer, but have changed, it is not a part of net work. How do I get connected with the network. it always looks for the network and can't find it so won't connect with just a modem.

Is there any other computers connected and works properly? Did you try to boot in safe mode with networking and Clean Boot to see if the issue persists? Please check the steps in the following guides: Troubleshoot Internet connection problems Wired and wireless network connection problems in Windows Sabrina TechNet Community Support