On the new, Windows 8, computer.
But this problem is, from the web searching I've done, a long standing one with easy transfer, existing since at least as far back as 2008, when people were transferring from XP to Vista.
The transfer of everything "public" on the old machine went fine, the transfer of the stuff on the named library all failed. As far as I know, there is no password there, but if there is, it would almost certainly be one of the ones I tried, because I only use hardcore passwords on a very few accounts.
I can access the files on the old machine just fine, but I can't figure out how to get the old machine to cough up the password, or how to work around it.