A free disk encryption software for Pocket PC, creates 2 MB storage (container) on your device.
This container can be of fixed or re-sizable size. They can be loaded/unloaded manually or automatically.
Cypherix PPC also lets you compress the files stored inside, to save space on your Pocket PC.
I currently have 3 folders holding about 20 pics and 12 documents.
http://www.cypherix.com/index.htm