Step-1 : Switch off the router and then switch it on after some time , within the first few seonds of booting press the CTRL+Break Keys
The router will enter the ROM Monitor mode .
Step-2: In the ROM Monitor mode change the configuration Register to 0x2142 to ignore the Startup Configuration file upon booting
Rommon2>b(For initiating the boot sequence)
On Booting the router will enter the Setup mode .
Would you like to enter the initial configuration guidelines (yes/no):
Step-3: Dont select any option (Yes or No) , just skip the setup mode by pressing CTRL+C.The router will now enter the User Exec mode
Step-4:Enter the privilige mode and copy the startup configuration file to the RAM(Running-Config)
Router#copy startup-config running-config
Step-5:Change the enable/enable secret or whatever password you want to change and then the configuration to the NVRAM
Router(config)#enable secret Cisco
Step-6:Dont forget to change the config-register value to the default
The procedure is quite useful in case someone has lost the password and wants to break it without affecting the rest of the configuration .