I have tried to install IPv6 on my Windows XP laptop using the command line “ipv6 install” and it failed with the error message “Failed to complete action, Error 0x800704b8”. When I tried to do it via GUI and it showed an error dialog box “An extended error has occured”. After some googling, I solve my problem with the following command:
esentutl /p %windir%\security\Database\secedit.sdb
Try to run the ipv6 install again and it works like a charm!