Please make sure that you are connected to internet. To make sure what you can do is
1. Go to run
2. Type cmd
3. In Command Promot, Type ping google.com -t
If you are getting continious IP of google means there is no problem but if you get 'Request Timeout' then that means you are not connected to internet.
If you are using Dongle of any company, Please call them and let them know. If you are using cable net, Please contact your operator and let them know.
I hope it helps you.
Please accept the answer if you are ok with it.