I like to skim through old stuff. I've been using a computer to write since I was 12, and so everytime I got a new computer I would just transfer all the old stuff. There was the debaucle with trying to open WriteNow (anyone remember that?) files with Word, but I mostly got over it.
I go through to see what I can steal from myself. For such poor writing, some of my characters and their relationships were surpringly well developed and I like to steal bits of that.
It's also good to see if I can spot why the old stuff is bad...and hopefully if I have not eliminated it, I can do that now. In addition, it's fun to surprise yourself with things you've created but had completely forgotten about. Write enough thousands of pages over the course of a few years and your bound to forget things and finding them again is like reading someone else's work.