WriteMonkey

When you need to clear your mind (and peripheral vision) of distractions and get some writing done, a minimalist writing app can be your best friend. For distraction-free writing in Windows, I love WriteMonkey. While you're writing, it hides all the formatting menus and just about everything else by expanding to full-screen mode and filling your screen with the background color of your choice. It doesn't do much formatting at all, but it creates an awesomely blank canvas on which to unleash your creative mind.

Note: This program is donationware. It is free to try, but the author accepts and encourages donations towards further development.