Microsoft started implementing this protocol since Windows Vista. IP v6 is a new network protocol, announced in 1988 and it was designed to increase amount of internet addresses. But though it was announced in 1998 it is still not widespread. And sometimes it can even cause troubles in networking and accessing the internet.

To disable IPv6 protocol go to Start menu -> Control Panel -> Network and Sharing Center in Vista. And go to Start menu -> Control Panel -> Network and internet -> Network and Sharing Center in windows 7. Then click Change adapter settings:

And in the following window right click on Local Area Connection and select Properties,

In the Properties windows uncheck the Internet Protocol Version 6

And click OK.