This article describes step-by-step instructions for how to disable Microsoft Internet Protocol version 6 (IPv6) or its specific components in Windows 7, in Windows Vista, in Windows Server 2008 R2, and in Windows Server 2008.
We do not recommend disabling IPv6. For more information, see the "What are Microsoft's recommendations about disabling IPv6?" question in the following article:

IPv6 for Microsoft Windows: Frequently Asked Questions (http://technet.microsoft.com/en-us/network/cc987595.aspx)

If you must disable IPv6 or components of IPv6, use the following steps. They outline the recommended method. To disable IPv6 or its components, you must be logged on to the computer as a member of the Administrators group, or your user account must be granted permissions to edit the Windows registry.

For more details visit http://support.microsoft.com/kb/929852