Some of these steps depend on how you think you'll use your device after rooting. I'm going on the conservative side to keep the instructions "simple". I strongly recommend updating to 1.2.2 before rooting. If you don't you will get error messages any time you use Wi-Fi. Everything that worked on 1.2.1 can be made to work on 1.2.2.
1. Prepare NookManager card
Follow instructions in the first post of this thread. Download the image file to your PC. You will need a disk imaging tool to burn the image to an SDcard. Here is a link to version 0.9 of Win32DiskImager: https://sourceforge.net/projects/wi...hive/win32diskimager-v0.9-binary.zip/download
. Unzip. Newer versions are more complicated. It has been said that best results are obtained when you run the disk imaging program as an administrator (right-click, "run as administrator"). If you are successful in burning the image you should see the directory contents for the SDcard under Windows Explorer as listed in post #531 above.
2. Update/customize NookManager
NookManager needs to be updated to work with FW 1.2.2. Follow the directions in this post: https://forum.xda-developers.com/t/nst-g-updating-nookmanager.3873048/
. At a minimum you need to perform the steps listed in the first section "Updating for FW 1.2.2". Read through the rest after that and decide if any of those things might be helpful based on what you think you'd like to do. If you do nothing, the original contents of NookManager will be installed including the dead Amazon App Store app and a very old version of ReLaunch. Of course once you are at that point you can always just uninstall and install whatever you want, so it may not matter to you.
3. Download the FW 1.2.2 update from B&N: https://su.barnesandnoble.com/nook/nook2/1.2.2/351e26527e80156183e74be2da2ce89f/nook_1_2_update.zip
4. Factory re-image
Also sometimes called a "hard reset", this returns your device to its condition when it was shipped out from the factory. This is good for devices that have been tinkered with in the past but is also not a bad idea before an update and is required to update a device that has been rooted. The good news is that NookManager can be used to trigger this process rather than trying to achieve the 8-failed-boot-attempts.
Power down your device and insert the updated NookManager card. Power up and wait for the program to initialize. Select "continue without wireless" (right lower hardware button). The Main Menu screen shows the current FW version at the top. Select "Rescue" (upper left hardware button). On the next screen select "Restore factory .zip" (lower right hardware button) and follow the screen directions. When the device reboots leave it at the "welcome" screen and attach it to your PC with the USB cable.
5. Update to FW 1.2.2
When you attach your device to your PC via USB you should be able to see the "Nook" drive in Windows Explorer. Drag the 1.2.2 update zip to the Nook drive and let the device (still on the "welcome" screen) sit. It will eventually sleep and during that time the update will install. If you come back to check on it and you are not sure if the update occurred, look at the Nook drive. You should not see the update zip file that you dragged over. Once that is done, continue with and complete the setup and registration process.
6. Root with NookManager
Power down the device. Insert the updated NookManager card and power up. Skip wireless. On the Main Menu screen it should now show FW 1.2.2. To root, select "Root" (upper right hardware button) watching for any error messages in case you made a mistake in updating/customizing the card, and then return to the Main Menu and Exit (lower left hardware button), following the screen prompts.
That is it!