an XipRegion is a section of the WindowsCE ROM.
PocketPC 2003 has these XipRegions:
XIPKERNEL, KERNEL, OS, SHELL, BROWSING, COREAPPS, EXAPPS, PHONE, MISC
PocketPC 2002 has these XipRegions:
OS, SHELL, BROWSING, COREAPPS, SYNC, 24MAPPS, 24MCONSUMER, MISC
SmartPhone 2002 has
SMARTFON, OPERATOR, OEM, LANG
individual regions are upgradable by means of a signed xip file. currently this upgrade mechanism does not seem to be used in practice.
each XipRegion starts with a signature 'ECEC' at offset 64 from the start of the block, this signature is followed by a pointer to a ROMHDR structure, followed by a list of modules and files contained in the XipRegion.