Some security options greyed out

[reposting since message never showed up after 8 days]

In Windows XP Pro, SP3, I connect to our company's domain sometimes using a
VPN. Some local security policies were set for me at that time, but I
don't usually log in to any domain.

Since I am a remote user, my userid has now been changed to be a member of
a group that doesn't have the policies applied.

Now, I would like to turn on some security settings that are unavailable to
me: Such as "Interactive Logon: display user information when the session
is locked". This is set to "not defined", and when I double-click the
item, it shows "user display names, domain and user names" but the drop-
down box is greyed out and I can't change it.

How can I change this policy setting?

I tried to figure out which Registry entry controlled this setting, using
some of Mark Russinovich's tools, but it appears that the "HKLM\Security
\Policy" key is being read... and all of its sub-keys are encoded so their
use is not obvious (which is understandable).

I appreciate any help. Thanks.

David Walker