[Nook HD, HD+ Q&A, Help & Troubleshooting] dbh369:
Introduction I wanted to put this into a thread since there are multiple questions about the same topics here. I'm simplifying here, Verygreen and others could give you a lot better detail. But if you are confused about some of the directions in other threads, this may help.

For most purposes, the SD card is treated as a simulated hard disk. So much of the control and terminology used is the same as HD.

For the Nook HD/HD+, the easiest (and so far only) way to access control of the machine is through an SD card. This is because the bootloader will check the SD card and boot an acceptable OS it finds there. So for now at least, ALL CM versions for these Nooks will be booted off the SD card. For those familiar with flashing their phones, it is no different except all ROMs will reside on the SD card. The internal memory, called EMMC (or internal SD) is available for use with these ROMs as of 12/28 releases so it isn't wasted, and data (not programs) you want available from both Stock and CM can be placed there.

ROMs are placed into memory with a program generically called Recovery. This is a small OS which can provide access to memory, update ROMs, wipe memory partitions, make backups of your ROM, provide access to partitions from your computer via ADB, etc. The version that we are using here is called Clockwork Mod (CWM). You will need to load this into the boot sectors of your SD card.

Burning CWM In order for the bootloader to load this program, the exact placement of bits in the SD memory is critical. So instead of copying this program over to the SD card, you must burn an 'image'. This is an exact replica of the specific bits mapped to correct sectors of the SD card. The term is usually 'burn' an image. To burn an image from Windows, the recommended program is Win32DiskImage (http://sourceforge.net/projects/win32diskimager/) but other "image writing" software will work.

When you write an image, your SD card will contain a partition exactly the size of the image you just wrote. A partition is a formatted and ready to use portion of a hard disk or something simulating a hard disk like your SD card. In windows, you might have seen instances where multiple partitions are allocated to different drive letters (e.g. C: and D: ) both on the same physical device. In Unix or Android, partitions are often known by names such as /system or /sdcard. However, native Windows installs are only able to see the first partition of a SD card. Therefore, if you write a 500MB image to a 32 GB card, at that point in time only 500MB is usable and 31.5GB is no longer available. For the CM10 installs on this thread, the rest of the card is automatically partitioned as new drives for the ROM and DATA and so becomes available (linux/android don't have the partition disabilities of Windows).

If you are using Leapinlars' CWM zips to root, etc, you can simply copy the files over after writing the image. There is room in the imaged partition for these files. IF you are using Verygreen's CM10, and possibly others, you can't copy the files over as the CWM partition is too small to start with. After the CM10 SD boots in the Nook, it will create partitions to use the rest of memory. But these new partitions are not easily accessible with Windows. This is why Verygreen's instructions include using ADB to push the zip file to the /sdcard partition.

Partitions For those writing CWM images for update zips (e.g. http://xdaforums.com/showthread.php?t=2062613), you will either want to use a smallish (e.g. 4G) SD card or repartition the card after you are done. The images by Leapinlar are large enough to load a few zip files for flashing in addition to the CWM program and a couple of backups (sometimes called 'nandroids'). But if you want to access the rest of the card, you'll need to repartition. The main reason you would want to do this is to return your 32GB card to full size, either with or without CWM on it; simply reformating on windows will not restore the unused data. For this, you will need to use a partitioning tool like Easeus (http://download.cnet.com/Easeus-Partition-Master-Home-Edition/3000-2248_4-10863346.html) or Minitool (http://www.partitionwizard.com/download.html). Note, this is generally NOT needed by the instruction sets on these fora, but is just provided as information, or if you wish to return to SC card to an initial state.

Copying files to partitions For the Nook HD/HD+, you must have the boot partition in the first partition of the SD card. This will NOT be the /data partition or the /sdcard partition. Therefore, you need a way to write to these partions on the CM builds. The easiest way is to boot CWM and use your computer to write to the these partitions via Android Debug Bridge (ADB). The process is boot to CWM, then go to mounts and storage, mount the /sdcard, THEN adb with CWM running and copy the zip over. ADB is a command shell that can execute commands on a remote android machine. Leapinlar's tips thread http://xdaforums.com/showthread.php?p=34168454#post34168454 gives a lot of detail about setting it up and getting it to run. If you are using Windows, there is a way (Update: this does work to see the sd card partition on CM10 SDs) to see all partitions on a SD card. See this tutorial: http://xdaforums.com/showthread.php?t=1585572. When done properly, you should be able to write your zips directly to the /sdcard partiton of the sd card (if that sounds confusing, please reread all that stuff above.) Note, there are partitions formated in unrecognized formats which are NOT seen with this method.

SD Formats SD cards are 'formatted' in different ways, just like hard disks. Formatting refers to data structures and directory structures used to keep track of files on a hard disk. In fact, any hd format can be used, but the typical format (data/directory structure) on smaller SD cards is FAT32. These are limited to a max filesize of 4GB and are fully compatible with Windows XP. For the larger cards, they often come formatted to a new format called exFAT (extended FAT). These allow larger files but are not native to Windows XP. However, a driver is available from M$ that will support exFAT. Because it is unexpected, you will get an error talking about the likely damage to your hardware if you proceed when writing an image to the exfat formatted SD card. You can ignore the error, the image is written bit for bit correctly.

Lastly to completely reboot the Nook HD/+, you need to hold the power button down for 10 seconds ignoring all prompts. Then hold it down again until it turns on.

I hope this is helpful. Please feel free to post comments and corrections below if I've made any mistakes and I'll update the op. I'll also try to answer questions if you have them.