A common problem which can stop your internet from working
in windows xp and windows vista is corrupt winsock. This is a problem which can
very often come about after attempting to clean up virus or malware infections.
This can also affect other versions of windows however operating systems after windows vista has built in winsock repairs so those should fix themselves once a problem is detected. So you really shouldnt need to worry about them.
There are tools that can be downloaded to reset system winsock, micorsoft themselves offer one of these which can be downloaded here. http://go.microsoft.com/?linkid=9664547
However since if you have this problem you can't access the internet to download these tools and chances are if you have the fault and are reading this you are doing so from your mobile phone or tablet we will assume you can't download those tools which isnt a problem we can do it manually.
First hold down the windows key and press the letter R on the keyboard
A box will appear to type a command in, you should type "cmd" and press the enter key
Winsock repair part one.
You should now have a black screen with white text and a flashing curser to type with. Now enter the command "netsh winsock reset"
Winsock repair part two.
Now the next step is slightly different if you're using vista or xp.
If your using windows vista, type, "netsh int ipv4 reset" or "netsh int ipv6 reset" if you are using ipv6, chances are if you don't know, you are not using ipv6.
If your using windows XP type, "netsh int ip reset c:\Reset.txt"
That concludes the winsock repair, in XP you may now wish to restart the PC and in Vista run the connection repair tool and the internet should then be working again.