Can't delete message becuase digital ID not found

[Don]

I have an email message in my Deleted Items folder that I
want to permanently delete. When I try to delete it, I
get the following message (Outlook XP):

Your DIGITAL ID name can not be found by the underlying
security system

The digital ID that was used no longer exists on my PC,
so reinstating it is not an option.

Does anyone know how I can go about deleting this message?

Thanks!