Now you can change the primary dns (index=1), assuming that your interface is static (not using dhcp)
You can set your DNS servers statically even if you use DHCP to obtain your IP address.
Example under Windows 7 to add two DN servers, the command is as follows:
netsh interface ipv4 add dns "Local Area Connection" address=192.168.x.x index=1
netsh interface ipv4 add dns "Local Area Connection" address=192.168.x.x index=2