1.) Make sure your conf register is 0x2102
Do show version and at the very end of the output you will see the Configuration register.
show version
Configuration register is 0x2102
If the config register is not 0x2102 then enter this command:
r1#configure terminal
r1(config)#config-register 0x2102
r1(config)#end
2.) Let's Erase the NVRAM/flash........
It is a bit different and annoying here for these types of routers/models as you need to physically remove the CF (Compact Flash) and only then, will it enter ROMMON mode (Ctrl + Pause remotely over the console will not do it for us). This means you cannot do this remotely, or at least not without the help of a remote/physical helper.
Step 1.) Power off, router and remove CF Disk Slot#2
Go to the router and remove the slot#2 cover uses your hand or it may help to use a........
It is common that you may get access to undocumented equipment and need to reset the password. This applies to many Cisco routers whether 2600, 2900, 3900 etc...
Cisco's Guide says to hit Ctrl +Pause/Break but if it doesn't work on some devices causing people to say "cisco password reset pause break does not work", you can see Cisco's alternative key combinations here:........