(Cisco Controller)> - is this just the prompt you are seeing ?
If so unless you have the enable password I don't believe you can set it factory default.
So to get to enable mode you need to do a password recovery first. See this link for details -
http://www.cisco.com/c/en/us/support/docs/routers/2500-series-routers/12722-pswdrec-2500.html
once you have done the above you can then do a factory reset although you may not need to as you may simply be trying to gain access to the router to be able to configure it.
Jon