Windows 7 Menu and settings UI are little bit different from that of the previous version of Windows. Unlike in Windows XP, in Windows 7 the controls are grouped according to the category. Changing the DNS is quite simple in Windows 7 if you could locate your Network Adapter settings. This tutorial will guide you to change the DNS of an Interface in Windows 7.
Change DNS - Domain Name Server on Microsoft Windows 7
Click on Start Menu and Choose Control Panel.
In the Option Network and Internet select View network status and tasks.
In the left side tab, select Change adapter settings.
This will display a set of Interfaces in your computer like Ethernet, Wifi, Bluetooth etc. Choose the one you are using to connect internet, right click on it and select Properties.
Now in the Properties window, select Internet Protocol Version 4 (TCP/IPv4) and click on Properties.
In the second half of the page, you can see the DNS settings control, there are two options to specify your DNS, leaving it automatic will either take the DNS from the Router setting or from ISP or you can manually specify the DNS address.
After changing the value, click on Ok Button. There is no need to restart. The settings will be applied on clicking the OK button.
To change to Google Public DNS
Preferred DNS Server : 8.8.8.8
Alternate DNS Server : 8.8.4.4