Just wanted to pass this on in case someone else has experienced it or as an advisory to prevent it from occurring....sorry, its a bit long.
I recently replaced an older machine and handed it down to my daughter. This machine had undergone a Win 7 upgrade from the original Vista OS it came with. During the last few months it has announced on my wife's work account that it's password needed to be changed. This was odd to us, since we do not use passwords here in the house, and have never used them on this particular box (mobile systems are another matter...). I addressed this using the OS tools for user accounts and repeatedly told the system there was no password. Occasionally it would crop backup, which I found irritating, but not deathly so.
Flash forward to setting the system up for my daughter. One day the system announces that I must change the password or I will not be allowed in. Of course, we have no idea what that password is, so now we're locked out of the system. I have no password reset disk, having never set a password. "No Problem" I thought, "we have an admin account, I can go in that way and adjust the User Account."
Heh, joke on me....in Win 7, the Admin account is there, but is disabled by default as a security measure. One must go in through the "Run" interface and turn it on (easily done and you can google the commands --if you can get into the system). I had never noticed the Admin icon had gone, mostly because I'm an idiot. So now I'm basically screwed. Quick, I go on line and start looking around....sure enough, this is a known anomaly of Win 7 (all versions, premium and up), and no, due to Security, MS is not going to provide you a crack to get in.
Fortunately, since this is a known problem, other folks have various crack utilities. "I'm saved!" I announce to my wife, who as a Lutheran has some odd ideas on my Baptist background, but nonetheless is pleased for my immortal soul, until I happen to mention it's the computer I'm discussing. Now convinced I'm going to Hell, I ignore her and go to CNET, which has various recommendations, download one of their suggested tools, and after going into Safe Mode, I'm into the system. Quickly I delete the offending account, and start to reconfigure the system for my daughter, as intended.
At some point, we reboot the system. After coming back up, guess what, I'm locked out again as the box, using the deleted account, demands a password. Quickly, back to the crack program, except now -- no account to crack!!! My daughter, who at this point held me in some sort of automation awe....now thinks I'm a complete doof, and I was inclined to agree.
Bottom line, my only option was to get the original system disk, break back into the lower level commands, and reformat the disk. As it was, I was on the verge of doing that anyway and I have all the data backed up, so it wasn't really a big deal. Actually, it has improved the system tremendously in terms of speed. There was also an educational benefit as I took my 14 year old through the whole process, including reloading the original Vista OS, then obtaining the required Service Pak, and doing the upgrade to Win 7.
My problem with all this however is that I had the time to work it as it was not an essential system. Had it been our normal work system, this would have been somewhat catastrophic. It takes some time to completely rebuild.
On our new system, guess what....I was prompted for a password yesterday......