Is this via cable or wireless connection?
Try rebooting the router and see if that establishes new connectivity.
If not try this
Press windows key & "r" one together.
In pop up box, type "CMD" without the quote marks.
when black box appears
type into it: IPCONFIG /FLUSHDNS
(Press enter key).
Check if you now have internet connectivity by hovering over wireless icon in bottom right of screen;
I assume you're connected to the router OK.