Let's you clone a system's configuration and install it to other systems. Basically, it's just quicker than using an install CD. It's a bit limited in what 'extra' stuff it can contain, but is fairly quick at installing images on multiple systems.
Similar to the above, but not exact. It's a remote-install program, meaning you can install (unattended I think) an OS from over a network.
Pixie

Actually, I've never had the opportunity to do this, so someone who has first-hand experience will be better off explaining.
Another cloning utility. It allows the image of one system to be copied to others.
An attended installation is just that - an OS install that you attend (watch and physically input settings, etc.). Have you ever installed Windows on your Home PC? That was attended. An unattended installation is where you use a tool similar to the Winnt.sif file you mentioned and pre-configure the settings and save it to a disk. Then, simply load up the setup program and walk away, everything will go automatically.
Similar to a virus-scanner, but instead of being able to be run by anyone and look for viruses, it can only be run by an Admin and looks for protected system files that have been accessed 'illegally' or somehow changed/overwritten. If it finds such a file, it will restore it to it's original version by reading from a backup file stored elsewhere.
Tells your system what OS's are installed and allows users who dual-boot to select which OS to load at startup.
Hmmm...sorry, something just came up. I'll try to finish later if no one else can fill in the blanks, but have to bounce for now. Hope it helps!