What screen do you see when you logon? The icons or a username/password field?
Hit Ctr-Alt-Del twice, will bring you to a logon screen, type in the account names manually in there, and use the passwords you think it should have.
Did you play around with the accounts? Try to rename them or anything?
I have tried that a few times and it hasn't worked, follows the same logic as normal login screen. I have tried to rename and such, but it is useless because im on a limited account. My main problem is that i'm locked out of only admin account and the password doesn't work.