Rewrite. I know this one because it happened to me a long time ago when I wrote my first novel. My computer completely gave up on me and although a computer guy we knew was able to salvage about fifty pages from the hard drive (not sure how), the rest of the manuscript was gone so I had to start over. I've also had this happen to chapters and a few short stories over the years. Anything I really cared about was rewritten, and yes sometimes I do think it was better. Was it exactly the same? No. But it still held the same spirit and that was what was important. Of course now I backup everything religiously to the harddrive, my Dana, on hardcopy, and on disc. Rewriting isn't the worst thing in the world, though, and so I'd do it again if I had to, be it five pages or five hundred if the story was really important to me.