>>Hi Naomi,
>>
>>>Do you know what can I do and how can I fix the problem?
>>
>>check if someone modified the hosts file (C:\Windows\System32\drivers\etc\hosts) on your computer.
>>
>>Can you PING web sites? Can you ping an IP address?
>
>Can you please give me the exact instructions here?
>
>I'll check the hosts files in a second, thanks a lot.

Christof,

All files seem to be OK there - they all have the same modification date (2006). I don't know which files exactly have to be there and what should be their content.

The host file has only two entries

127.0.0.1 localhost
::1 localhost