William,

Thanks for the tip.  I've worked with these procedures before to scrape
hundreds of sites, so I'm pretty comfortable with mirroring password-protected
sites.

This case is different: I'm scraping my OWN site and I'm scraping a site that
gets its images from a separate WIKI server.  There's no point where I
explicitly request a file from the Wiki server (the images are simply linked
from my HTML files), so I can't add its URL (and the passwords) from the
HTTrack interface.  (In fact, adding the Wiki server to my list of URLs only
returns a mess of errors.)

If I browse this site from IE, all the images show up fine because I'm
authenticated in the machine's NT domain and have permission to browse the
Wiki.  

So I'm wondering if there's a way to set my local machine to be my proxy,
thereby utilizing my domain permissions.