My wife gave me a Nook Simple Touch this past Christmas and a few months back I decided to mess around and root it since it seemed like having it be a full fledged Android tablet would be pretty cool, but well, it wasn't that cool. At least I didn't think so. It slowed it down, wore down the battery life and most apps I tried didn't work very well. Turns out I really just like it for reading books, which its awesome at. So, time to undo the root. But how?
After looking around and trying a few things I was finally able to find a process that works. The first thing is to wipe the data directory by getting it to reset it. To do this on the Nook Simple Touch you have to do 8 uninterrupted starts. So first, hold down the power button (the one on the back) and turn it off. Then hold the power button on the back for a second again to begin to power up the Nook, after waiting a second or two hold both the power and home buttons simultaneously for 5 seconds or so until the screen flashes and it begins to start up again. I found I had to wait a few seconds after the screen turned back on after each flash before holding the buttons again in order for it to reset again. Keep reseting it like that until a restoring screen comes up and it wipes the data drive.
At this point it is still rooted. In order to restore it back to defaults turn it off again and then after hitting the power button again to turn it on immediately hold the two lower "page back" buttons on the lower left and right side of the device. A screen will come up asking if you want to restore the device to default settings. Confirm twice and the Nook will reset. My Nook is now back to its old self, yeah!