Password Recovery for common Cisco Routers (1700/2600/ISR etc)

Boot the router and interrupt the boot sequence as soon as text appears on the screen.
Press Ctrl + Break for SecureCRT in Windows.
It will go to rommon mode
rommon 1>

Change the configuration register to ignore the contents of NVRAM
rommon 1>confreg 0x2142

Reboot the router
rommon 2>reset

Router will boot as a new router. After booted, you can either delete startup config file in NVRAM or copy startup-config to running-config and change password.

Finally change change the configuration register back to its default value before reboot.
Router(config)#config-register 0x2102