They are all AD Security Groups. The AD Browser should load correctly if you put the admin password into the AD section (you need to do it each time to reload that page).
If it still doesn't load, try doing some http://www.edugeek.net/forums/home-a...debugging.html
two other questions-
1. If all I want is the option to give access from home to files- do I still need
the same installation and setup, or is there a way to simplify this?
2. must the AD connection be made by a Domain Admin?
what if we want to have another domain user manage HAP?
1. It's the same install process, you can just omit entering anything for the AD OUs or the unwanted feature tabs
2. Yes, it's only for AD Look ups and password resets, the user impersonates his/her self so they are connecting to AD using their own context