CISCO Router 1841 Resetting to the factory Default

Hi,

I can’t able to connect to one of my Cisco Routers (1841) either thru console or tru telnet. I changed the memory and still i couldn’t able to connect. So please help me in this regard as my network is down for a while.

I need to reset it to a fcatory default and then i can do the confgiuration.

So please help in this regard

Thanx

Sabir