Darth Bizarro said:
When the old EU was being developed, the PT era was considered off limits by Lucas since he still held on to the possibility that he would make 1, 2, and 3. Though this did eventually happen, I often wander how well a set of novels by, say, Timothy Zahn telling the story of Anakin's fall to the dark side might have turned out.
It was off limits, but it's interesting what little items the old EU writers assumed and put into their work. See this thread: http://originaltrilogy.com/forum/topic.cfm/The-Prequels-as-Envisioned-by-the-Pre-PT-Expanded-Universe/topic/14053/ for some info.