Hi ak,

this is by default not possible.

You could create an own Outlook contact form and this form can be password
protected.

But why do you want to protect your contacts? If you do not want to share
your contacts you can change your seettings, that nobody see your contacts,
but if a user has the rights to share your contacts you want to limit this
with a password?

--
Oliver Vukovics
Share your Outlook PST files without Exchange: Public ShareFolder
Synchronisation for Outlook and Exchange: Public SyncTool
http://www.publicshareware.com