Is this happening wired, wireless or both? Look in Control Panel>Device Manager and check the Properties pages of both the network adapters.
Under the Advanced tab, check the wireless that Roaming is set to Normal and wired for Duplex to make sure it's set to auto negotiation.
Also, press the Windows key and R then in the Run box, type
cmd /k ipconfig /all
then press the Enter key.
From the black form, take the Default Gateway address, put it into your browser URL bar and see if you can get into the router's settings. Login details should be on the label.