[Halcyon]

I would never do any installations of an operating system without atleast backing up as there is always a possibility of your data going.
Stick a few blank DVD's in and backup your important data.

I've never heard of the unattended mode, but I'm sure that someone will post with some more info.

Your best bet for the future would be to get hold of Ghost and do an image of your fresh new system with all drivers, etc.