All you have to do is type “Network and Sharing” in your start menu textbox and click  then “Click “Change adapter setings”.
Right click your network adapter, and pick properties.
Find Internet “Protocol Version 4 TCP/IPV4” and click it from the list then click properties button.
Lastly, in the DNS bo, select “Use the following DNS server addressess”
Type in 8.8.8.8 in the first box and 8.8.4.4 in the second box. Click OK
If you want to change your routor’s DNS go to your routors webstie which usually has an address like 192.168.1.1 .
Look for the DNS section and type in 8.8.8.8 in the first box and 8.8.4.4 in the second box and click ok.
Google Claims that their DNS will speed up and secure your web browsing experience.
http://code.google.com/speed/public-dns/