What can I do to trace the origin of a DNS resolution in Windows 7?
Solution 1:
It's probably the NetBIOS name cache. Try purging it using nbtstat from an elevated command line window:
nbtstat -R
You might also wish to disable NetBIOS. This option is available on the WINS tab of the Advanced TCP/IP Settings dialog.
Solution 2:
Running nslookup will show you the name resolution using responses of the current (normally the "primary") name server.
It's my normal first step when troubleshooting name resolution problems in Windows, especially when messing with HOSTS file entries and having to flush the dns cache.