The following procedure is pretty standard and works on most Cisco devices.
- Connect to the device via it's console port setting your terminal emulator to 9600/8/N/1 and power cycle it.
- As soon as it starts to POST, send it a BREAK signal (depends on your terminal emulator) to drop it into ROMMON.
- At the prompt, type confreg 0x2142
- Then type reset and let the device reboot completely (do not use ctrl-c to skip config dialog).
- After the device comes up, go into enable mode
- copy startup-config running-config
- show run to make sure it looks good.
- Go into config mode (config t)
- Enter the new secret password (enable secret)
- Make sure to do a no shut on all the interfaces that should be up.
- Type config-register 0x2102.
- Type end to exit config mode.
- Save the config using write mem.