Cisco 1721 router problem

Does the router boot to rommon mode everytime you turn it on?

There are two reasons why the router could be booting to rommon mode

1. There isn't a valid ios image loaded in flash memory
2. The configuration register is set to a number that ends with '0'

Change the configuration register setting to a number that ends in '2'. (i.e. 0x2402)

You do this with the command: confreg 0x2402 <hit enter key> (in rommon mode)

Reboot the router and it will first search for boot system commands in the startup config, if none found it will boot to the first valid ios image in flash memory.

If there isn't a valid ios image in flash memory, the router will continue to boot to rommon.