Installation and security problem

Windows XP laptop.
I'm trying to remotely troubleshoot an individual's
installation problem. He's trying to install a plugin to
Outlook and it fails with a ".dll failed to register"
error (HRESULT -2147024891). When he tries to install
another, separate program (an IE plugin unrelated to the
first) he gets this message: "Could not write value URL to
key.." with the path and a "Verify you have sufficient
access to that key..." So we first verified he was using
an account with admin privileges (he is). Then we ran
regedit32 to look at the Registry and view the permissions
as we got "Unable to view security permissions."

Any idea what's going on here?

Thanks,
Keith