Welcome
c233liu,
first thing you can do is click on yellow triangle (from your image) in network and sharing center to start troubleshooter.
if that doesn't help try unpluging your Modem or cable from telephone line and plug it back.
also if still no response try setting your network adapter under
Control Panel\Network and Internet\Network Connections >> right click adapter >> properties >> Internet protocol 4 (IPv4) with folowing settings from this image:
if all that does not help press
start, type
cmd and press
enter.
type into console
ipconfig /all and post the output
Also how are you connected to the net?
I'm assuming all you have is a cable?