Well, if you have telnet access to the router and its IOS, and there is already a Privileged Exec mode password set (this can be checked by trying to enter said mode via the 'enable' command from the lower User Exec mode), then AFAIK, the only way to reset the passwords is to clear the startup configuration file, effectively clearing all configurations made for that router (this includes all routing protocols, routing tables, IP addresses and subnet masks, et al.) - and reloading the entire IOS from factory settings. is this what you wish to do, or does the router actually have a critical role, in the sense that wiping everything would get you some serious flak? Of course, if you can't access the router IOS via telnet (asking for username/password on the go), you might as well be stuck.