Please Help! Log-on Password Problem

[Mike]

Today I tried logging on to my laptop and a new "guest
user" user was on screen and I was being prompted for a
password on each of the usre's. I never set a password
on my laptop. It will not let me log-in without a
password, but there isn't a password?? I tried booting
up in safe mode, I tried cnt-alt-del to sign on as system
admin, but still a password is required. Please help!!
What can I do??

 

[Mike]

Jupiter: I can't get past the password even if I leave
it blank. No one has gotten into the computer here. Is
it possible someone got into it while I was on-line via
my wireless connection? I last used it about four days
ago and simply shut it down. I try now and it does this.