All Cisco 1900 Series Integrated Services Routers (ISR) have modular design that allows for reuse of a broad array of existing modules that meet business requirements while maximizing investment protection. Among all Cisco 1900 routers, CISCO1921/K9 and CISCO1941/K9 are best selling models.
Forget your password as some reasons, and don't know how to recover them, this article will help you.
Visit the blog: http://www.3anetwork.com/blog for the details of the password recover steps,
The steps of the Cisco 2900 password recover is similar to the Cisco 1900. Once the Cisco 2900 router is on Rommon mode, reinsert the compact flash, and you can follow the steps 4-15 as recover password of Cisco 1900.