The Internet is in transition. By the end of 2011, there will be no more Internet Protocol version 4 (IPv4) addresses and will be replaced by the next generation Internet Protocol version 6 (IPv6).
Setting up your computer to prefer IPv4 over IPv6 is a temporary solution so that your computer will be able to normally function in a native IPv4 network without dual stack.
NOTE: Dual stack means that devices on the network are able to run IPv4 and IPv6 in parallel. It allows hosts to simultaneously reach IPv4 and IPv6 content, so it offers a very flexible coexistence of both. For information about dual stack implementation, click here.
Windows Vista and Windows 7 operating systems also feature dual stack which allows your computer to run using IPv4 and IPv6 simultaneously. However, there may be instances that you will encounter problems in accessing dual stack networks. If you wish to disable/enable IPv6 components and prefer IPv4 over IPv6, refer to Microsoft Support for more information.