The older Nook models including your NC have separate storage partitions for apps and user media content (e.g., books, music, videos, etc.). Even if you can remove unused stock ROM apps it won't help freeing up space for more media content. Some XDA developers have created a method to resize these partitions to yield more space for user media content, see
http://forum.xda-developers.com/show....php?t=1094371 -- it requires great care in execution as mistakes can permanently brick your NC.