If you're running Windows 7 in a networked environment, by default you have an auto-configured IPv6 connection to your network. IPv6 is the next-generation addressing system planned for the Internet, necessary because the current addressing scheme, IPv4, has run out of addresses.
Unfortunately, IPv6 still has security holes and provides an opening for attackers to compromise your network. For now, most ISPs are using workarounds and still rolling with IPv4.
Unless you're working for a large company, you likely don't have to worry about IPv6 yet. If you want to just shut it off, here's how to do it.
First, in Windows 7, click Start and type into the search box:control panel
Now, from the Control Panel, select Network and Sharing Center.
On the next screen, click the connection you want to modify.
A status display for that connection will come up. Select Properties.
Next, you’ll see a property sheet for the network connection. Uncheck the box next to Internet Protocol Version 6; that is, TCP/IPv6.
Note: You'll need to do this for each network connection on which you're disabling IPv6.
And that's all there is to it.
If you're a Windows user, check out how to disable IPv6 in Windows 7.