Note: This procedure is applicable to most Cisco routers, however the key is knowing the register to use.

Turn the power off.
Turn the power on.
About when you see the following message, hit Ctrl-Break (yes the Pause/Break key).

Readonly ROMMON initialized

You should be presented with the following prompt:

rommon 1 >

Enter confreg 0x2142:

rommon 1 > confreg 0x2142

Then, you will get the following message:

You must reset or power cycle for new config to take effect

Enter reset:

rommon 2 > reset

The router will reboot and start the initial configuration wizard. Just say “No” to skip. This will drop you to a “Router>” prompt.

Enter enable, and you will presented with a “Router#” prompt.

Copy your startup-config to running-config (make sure you do not switch the order or you will lose your configuration):

Router#copy startup-config running-config

Then reset the password (I set it to “cisco” below.):

Router#configure term
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#enable secret cisco

Then, type the following:

config-register 0x2142

If you cannot remember the register number from earlier, you can find by issuing the following:

Router(config)#do show version

Enter:

Router(config)#end

And save:

Router#write mem
Building configuration…
[OK]

Then reload to test:

Router#reload
Proceed with reload? [confirm]