I disabled IPv6 on an SBS 2008 server to resolve an issue with the Exchange 2007 NSPI RPC endpoint. Please see:
After disabling IPv6 the server would hang at "Applying Computer Settings" for approximately 1 hour before finally booting.
If you ever disable IPv6 on an SBS2008 server you need to perform the following registry change!
1. Open Registry Editor and then the registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\
2. Double-click DisabledComponents entry. Create this entry if required.
3. In Create the new entry DWORD (32-bit) Value.
4. Type DisabledComponents, and then press ENTER.
5. Double-click to open DisabledComponents. Enter the value as "ffffffff" and then click OK.
This should do the trick. You will now be able to disable IPv6 and still boot into SBS2008.