> When you say "child links," do you mean any links from the starting page,
even if they are on a different server?> 
> E.g., if I run a test on serv.1.org/index.html which does not require a
logon, and I test a link on that page to another.serv.net/help.html, which
requires a login, can I just do user:passwd@serv.1.org/index.html (no login
actually required) and have that automatically appended to to any external
link?

I hope not - wouldn't that be a security issue?  The external servers would
receive the user:password string along with a referral header...?
Or perhaps the client (HTTrack) does not really send the user:pass but only
uses it when challenged for authentication.  In that case it would be a good
probably be a good thing to have. :)