1) Not sure how to retrieve your bookmarks; it depends on what you've done.
2) To try and prevent this happening again, use del.icio.us (sounds complicated but it's easy and free.)
It's a free online service that stores your bookmarks in public for you. So you can share your fave sites with everyone else. When on a page you want to bookmark, you do so in the normal way, and 'tag' them to remember them. For example, if you bookmarked this page, you may choose the tags 'answer' and 'help'.
http://del.icio.us
They also have a very good firefox extension:
http://del.icio.us/help/firefox/extensionnew
That way, even if your entire house is destroyed in some freak weather incident, your bookmarks should still be safe.