Delete / Erase / Change Password on Cisco 2600, 2800, 3600, 3700, 3800, series routers
Step 1: Hit ctrl / break directly after powering up the router.
Step 2: type: confreg 0x2142 from rommon 1>
Step 3: type: reset from rommon 2>
Step 4: Would you like to enter the initial configuration dialog? [yes/no]: answer NO
Step 5: type: en from router>
Step 6: type: COPY STARTUP-CONFIG RUNNING-CONFIG from router#>
Step 7: type: SHOW RUNNING-CONFIG from router#>
Step 8: type: CONFIGURE TERMINAL from router#> to edit or remove any existing passwords enter Global Configuration
Step 9: Type enable secret <password> in order to change the enable secret password or type NO ENABLE SECRET to remove the secret from router(config)#>
Step 10: type: NO ENABLE PASSWORD to remove the password from router (config)#>
Step 11: Type the no shutdown command on every interface that you use.
Step:Hit Ctrl / z" or endto leave the configuration mode.
Step:Type write memory or copy running-config startup-config to save the changes.