It has become quite general to boot into different versions of Google Android OS from a single device. Many devices are out there that have now been turned into dual boot. This feat is usually achieved through an AOSP based ROM that users flash and also an OEM-skinned ROM. But developers were definitely not content with that and have been pushing the boundaries for some time now. The HTC HD2 was the first device that was able to triple boot. And the boots were not just into different ROMs but in actuality three different operating systems altogether. This achievement, however, has been overshadowed recently by the quad-booting capabilities of the Barnes & Noble Nook Tablet.
An XDA forum member called malloneem has created a tutorial that shows users how to flash three different ROMs on an SD card while the stock Nook OS and software is left at the tablet’s internal storage. This makes for a total of four bootable ROMs.
As mentioned by malloneem, this procedure is done by using Windows and applicable to Nook tablet 8GB or 16GB variants. After the process is done, users can choose the stock Nook operating system or Cyanogen Mod 7, 9 or 10. Majority of the tutorial guides the users to run through a partition process which is designed to allow three ROMs to run from the SD card. After that ROMs can be chosen from various developers and installed. This is a time consuming process though so make sure you have ample time to carry it through. The complete tutorial can be found here.