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

To disable certain IPv6 components yourself, follow these steps:

1. Click Start à Run à type regedit in the Start Search box, and then click regedit.exe in the Programs list.

2. In the User Account Control dialog box, click Continue.

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

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

4. Double-click Disabled Components to modify the Disabled Components entry.
Note If the Disabled Components entry is unavailable, you must create it. To do this, follow these steps:

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

b. Type DisabledComponents, and then press ENTER.

c. Double-click DisabledComponents.

5. Type any one of the following values to configure the IPv6 protocol, and then click OK:

Type 0 to enable all IPv6 components.
Note The value "0" is the default setting.

a. 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.

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

c. Type 0x10 to disable native IPv6 interfaces.

d. Type 0x01 to disable all tunnel IPv6 interfaces.

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

Notes

· Using a value other than 0x0 or 0x20 will cause the Routing and Remote Access service to fail after this change goes into effect.

· You must restart your computer for these changes to take effect.