Disabling IPv6 on Windows 2008

   1. Open regedit

   2. In Registry Editor, locate and then click the following registry subkey:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters \

   3.      Double-click DisabledComponents to modify the DisabledComponents entry.

Note If the DisabledComponents entry is unavailable, you must create it. To do this, follow these steps:

In the Edit menu, point to New, and then click DWORD (32-bit) Value.

Type DisabledComponents, and then press ENTER.

Double-click DisabledComponents.

   4.       Type any one of the following values in the Value data: field to configure the IPv6 protocol to the desired state, and then click OK:

Type 0 to enable all IPv6 components. (Windows default setting) 

Type 0xffffffff to disable all IPv6 components, except the IPv6 loopback interface.

This value also configures Windows Vista to use Internet Protocol version 4 (IPv4) instead of IPv6 in prefix policies.

Type 0x20 to use IPv4 instead of IPv6 in prefix policies.

Type 0x10 to disable native IPv6 interfaces.

Type 0x01 to disable all tunnel IPv6 interfaces.

Type 0x11 to disable all IPv6 interfaces except for the IPv6 loopback interface.

Refer :  http://support.microsoft.com/kb/929852