One line of attack is to address the router. You can start by turning off encryption, setting it to a fixed channel and changing the SSID. If that doesn't work do a full factory reset and go from there. If you get internet access, then reconfigure your encryption and other settings, testing at each change to make sure you still have access.
But before you get deep into that, run the command
cmd /k ipconfig /all
and post the results here.
Have you tried connecting to the router with an Ethernet cable?