ROM = READ ONLY MEMORY
It is an "image" so you cannot change it.
Some odd devices (Symbol, Dolphin, etc.) have the notion of a "app install"
program that is built into the ROM. It will look at a certain directory for
a config file and .CAB files that should be installed after a device reset.
These files are located on changable areas (cards, etc.) so you can put what
you want there and have it get installed.
As far as I know normal end user PDA's do not support this type of feature
but I could be wrong.