I have no experience with Vista.
You could always do what I did when I first got XP- make real good friends with a guy at the GeekSquad after hours.
However, some measures after you do get it up and running again.
vLite is "a tool for customizing the Windows Vista installation before actually installing it." Requires you to have a clean install first before playing around to customize it. Or there is
Partition Image, also called PING, which can "backup and restore whole partitions, an easy way." You do not need to worry about using PING, so long as you don't experience what happened in
this thread.