By default all the supported features for IPv6 are enabled in Windows Vista and Windows Server 2008. However, if you are not using IPv6 yet then you don't need to be enabled at all or if you do use and want some of the components be disabled because you don't use it then this can be done Windows Registry.
The features/components that you can control in IPv6 from the Windows Registry include
Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)
6to4 based interfaces
IPv6 over all non-tunnel interfaces, including LAN interfaces and Point-to-Point Protocol (PPP)-based interfaces
Default prefix policy table to prefer IPv4 to IPv6 when attempting connections
The following procedure to edit the Windows Registry should help you control IPv6 capabilities in Windows Server 2008 & Windows Vista.
1. Click Start - Search and type “regedit”. This launches the WIndows Registry.
2. In the registry, navigate to the following registry key
3. In the right pane, right-click and select New – DWORD (32-bit value) and set its name as “DisabledComponents” and set its value as one of the following based on the requirement
“0″ – Enable All IPv6 Interfaces (Default)
“FF” (equivalent binary value is 11111111) – Disable All IPv6 interfaces
“2″ (equivalent binary value is 00000001)- Disable All 6to4 Interfaces
“4″ (equivalent binary value is 00000010) – Disable all ISATAP interfaces
“8″ (equivalent binary value is 00000100)- Disable all Teredo based interfaces
“10″ (equivalent binary value is 00001000)- Disable IPv6 over all non-tunnel based interfaces including LAN & PPP
“20″ (equivalent binary value is 00010000) – Default prefix policy table to prefer IPv4 over IPv6