Cisco router fails to boot IOS, it then boots into ROMMON Monitor (ROMMODE), what are the steps in troubleshooting this boot error?

first step: look in flash memory for a valid image : issue the command; rommon />dir flash :

if valid flash image is located, attempt to boot the image; issue the command; rommon/> bootflash:

second step: if configuration register is correct usse the # sh start command to check if there is an instruction for router to use a different location for cisco IOS image

0x2102: value indicates router attempts to load Cisco IOS image from flash and loads start-up config from NVRAM

0x2142: value indicates router ignores content in NVRAM

0x2120: value indicates boots into ROMMON mode