Hi, I had the same problem. I'm running Win XP (Pro) SP2. I fixed it
by enter the following command in the command prompt:
esentutl /p %windir%\security\Database\secedit.sdb
After that, installation of TCP/IP Version 6 worked fine.

Hope it will help someone,
Anders


That's brilliant! It totally worked. I don't know all that much about the
"guts" of MS but could you explain exactly what that command-line program is
and what it is that it did that allowed my winxp home sp2 to install ipv6?