Anyway, make sure to answer the question in the way that disables the thing. CWM should ask you at one point if you want to disable that protection mechanism I spoke of, I don't remember when it happens, perhaps only if you leave CWM via 'reboot system now' after installing TWRP. CWM's menu is navigated with the volume up and down keys, the 'N' button is enter and a short press of the power button is escape/back. You can use it to install the TWRP zip file from the SD card. It should boot automatically and present you with the CWM recovery. Turn off the tablet, put the card in, then switch the tablet on. After writing the image, copy the TWRP zip file mentioned at the beginning to the card, but this time don't extract anything, and don't change any files on the card. The card will be completely wiped in the process, so make sure you don't lose any important files. Unzip the file and (assuming you're running MS Windows) use Win32 Disk Imager to 'burn' it to a microSD card. The easiest way to create a bootable microSD card is to download this image file (NookHDplus-bootable-CWM-6028-for-stock-small-rev4-(05.15.13).zip from here). And a suitable card reader for your PC! You'll only need it for the installation procedure, you don't have to keep it in the tablet once CM11 is up and running. So, you will need a microSD card at least 256 MB in size, but better 1 GB or more, but at most 32 GB. That card will boot some older recovery, which you can use to install TWRP and disable the protection mechanism. If that happens, you'll have to create a bootable microSD card. Problem is, if I remember correctly the Nook has a protection mechanism that automatically restores its default recovery. If you're lucky, the TWRP recovery you just flashed should boot (at which point you can release the 'N' button). Power on the tablet while still pressing and holding 'N'. The app will offer to reboot into the recovery, but that function doesn't work on the Nook. Copy the file 'recovery.img' to your Nook, start Flashify and flash the recovery partition using that file. Download the custom recovery TWRP 2.7.1.0 from here and extract 'recovery.img' from that zip file.

If you already have root, you can try to flash a custom recovery using the app Flashify. The recovery is kind of a very basic operating system that resides in a special partition of the internal flash memory. To install CM, or any other custom firmware, the first thing you need to do is to install a custom recovery.

Cwm recovery zip nook color