If you internet stopped working, you can check it easily with following steps:
Retrieving connection settings
To diagnose the line, type the following command (Windows XP / Windows 2000) Start / Run:
cmd /k ipconfig /all
Verify that IP address is assigned. If this is the case, proceed to Step 2. Otherwise type the following command and repeat step 1:
cmd /k ipconfig /renew
not work, then the internet connection is not established. The problem may be drivers, an access provider outage or a hardware problem.
In the results of (1), retrieve the IP address of the default gateway and DNS servers, and then type the following commands:
ping -t adresse_ip_passerelle
If that does not work, then the problem is with the bridge.
ping -t adresse_ip_dns
If this does not work, then the problem comes from the name servers.
Checking Name Resolution
ping -t www.google.com
If that does not work, then there is a name resolution problem, either due to a bad connection setup (poor specification of name servers) or a problem with the ISP or a problem due a firewall.
Verification of applications
This is to check different applications using the Net to check if the problem is the software used:
Recover its connection after infection
After being infected with some spyware, it may be that you have lost your Internet connection. for this use any good Antivirus program