Was cleaning a Vista x64 computer and lost network connectivity. No DHCP connection, hard set an IP, still no ping out, con connectivity. Disabled internal NIC and added PCI NIC, same issue. Tried USB Ethernet adapter, same. Even tried USB wireless adapter. It saw the SSID and took the password, then no IP other than the 169. default one.
Ran Rkill, Rouge Killer, Malwarebytes, even Tweaking.com's repair suite. Removed drive and scanned with Vipre and TDSSKILLER. No rootkits.
So in desperation I imaged the drive and did an upgrade to Windows 7 Ultimate, SAME ISSUES!!
It's not location specific either because I have worked on it at two different places.
An ipconfig /renew returns "unable to contact your DHCP server".