If you download a firmware file for the 5320 (e.g., RM-416_07.13_prd.core.C00 ), you won't just see a single file. You will see a folder full of data, but the most important is often a file ending in .rpg or contained within a .rofs2 file. However, inside the core firmware package (the Core file), you find references to .
Installing a ROM RPKG on the Nokia 5320 carries some risks, including: nokia 5320 rom rpkg