Well using word "rom" i think about OS image - it is possible to load it eg to ram (but needs editing virtual memory map - for example cmonex from hpcfactor.com done it for nec mp900c). AFAIR WinCE can't use normal filesystem as normal Windows, it is always loaded from rom image (also on CEPC) - it can use disk as file and registry storage, but not for itself (that what we see in any file browser is mixed from files in rom and those on storage - to show that - total commander ce has nice option called "hide files in rom")