Starting in Windows Vista and Server 2008, Microsoft includes native support for IPv6 (Internet Protocol Version 6) and is enabled by default. IPv6 is the new computer address protocol that will eventually replace IPv4 which is currently the most popular standard. Unless you network has a specific requirement for IPv6, very few do, you can safely disable IPv6. Unlike other protocols, you cannot disable IPv6 by disabling the protocol on each of your network interfaces. While that will disable the protocol for the interfaces the loopback and tunnel interfaces will still have it enabled that can cause problems with applications. The proper way to disable IPv6 is to disable via the registry.
First, click on the Start Button and type in regedit and hit Enter.
Then, navigate through HKEY_LOCAL_MACHINE, SYSTEM, CurrentControlSet, services, TCPIP6 and Parameters. Right click on Parameters and select New and then DWORD (32-bit) Value. Name the new value DisabledComponents and hit Enter. Now right click on the new DisabledComponents value you just created and select Modify. Set the value of DisabledComponents to FF and click OK.
After a reboot IPv6 will be disabled on all interfaces.
This article was updated to reflect Microsoft's new guidance in KB929852 indicating DisabledComponents should be set to FF instead of the previously communicated FFFFFFFF. This will prevent a bootup delay of 5 seconds.