Well, Barbara Cartland did it, of course, but what about a novel of some kind of quality? Could you write it in only three days?
That's what Jennifer K. Chung did, when she participated and won the International 3-Day Novel Contest with her novel, which counts 20,000 words and around 100 pages.
How can you write a novel in such short time?
With all due respect to the Muse, a writer's best friend is really the deadline.
You can help yourself a lot by giving yourself a deadline to force your creativity and get things done. Obviously, novel writing software is another smart thing that will help you.
You can read the full article here:
http://crosscut.com/2011/01/31/books/20580/Write-a-novel-in-3-days--Bellevue-software-engineer-wins-first-prize/