Following is process to reset the password on Cisco C1841 Router,
Connect the console cable to Router C1841
Use the power switch in order to turn off the router, and then turn the router back on
Press Ctrl + Break on the terminal keyboard within 60 seconds of power up in order to put the router into ROMMON
Type confreg 0x2142 at the rommon 1> prompt in order to boot from Flash
*This step bypasses the startup configuration where the passwords are stored
Type reset at the rommon 2> prompt.
The router reboots, but ignores the saved configuration.
Type no after each setup question, or press Ctrl-C in order to skip the initial setup procedure.
Type enable at the Router> prompt.
You are in enable mode and should see the Router# prompt.
Type copy startup-config running-config in order to copy the nonvolatile RAM (NVRAM) into memory.
** Do not type copy running-config startup-config or write. These commands erase your startup configuration.
Type configure terminal
Type #enable secret
Type config-register #config-register 0x2102
Type write memory or #copy running-config startup-config in order to commit the changes
** Remember to the steps of config-register 0x2102 , otherwise it will stay on 0x2142 previously where each time router boot, it won’t load the startup-config, and prompt for initialize the router.