Windows 7 can't resolve DNS

While working on a client’s Gateway LT2030u netbook running Windows 7, I ran into an issue resolving dns names to IP addresses. The computer had been infected with a number of malware applications, including some Trojans and a large number of adware entries in the registry. But those were all cleaned up.

Despite several attempts to clear out everything, including:

• IPCONFIG release and renew
• removing NIC adapters and rebooting
• correcting the etc/hosts file

The computer still would not resolve a simple address like www.apple.com. IPCONFIG /ALL indicated that everything was configured correctly but Windows 7 still would not resolve the dns name.

Yes, a standard PING test to a physical IP address worked fine.

Repair Process

This is what I did and finally got it working. Running the command prompt as an administrator I then ran the following commands.

1) netsh winsock reset catalog
2) ipconfig /release
3) ipconfig /renew
4) ipconfig /flushdns
5) disabled the network adapter
6) enabled the network adapter

Then performing a simple ping test to www.apple.com Windows 7 finally resolved the dns name for this website.

This first step was the key to resolving the issue. Apparently a virus or some other malware infection had messed up the WINSOCK configuration so that the computer could not receive any updates and thus remain infected.

From another angle, we have also found DNS issue due to a Windows update that seems to change the default IP addressing scheme from IPv4 to IPv6. Many of the new routers support IPv6 but the DNS functions may now work correctly. Microsoft has posted an knowledge base article KB2533454 that explains how to set the IPv4 as the primary scheme.

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