I have two 3750G stacked and I am locked out of console access. The startup-config console settings are login and local. However, there is no local database, i.e, no username and password is specified. After attempting the normal password recovery (init_flash, load_helper, dir, rename, etc) and booting, the console screen still shows the "username" prompt. And since there is no username I am stuck. The switches are not currently in production so I can do anything to them to recover.
restart it and use the serial console to interrupt boot.
Once you're at the switch prompt, do the following:
Once it's booted, I'd suggest copying off the old config, modifying it with a user and then loading it back onto the switch.