Revert of Login Password

Does anybody know why my login password is reverting back to the last password I had? I am administrator at home on an iMac with OS 10.6.8, which also has three other non-Adm people (my kids). I recently (last 4 months) changed my password away from the password that the other users knew because I exercised Parental Controls. Now, two times recently my computer has reverted back to the old password, the one that everybody knows. The kid who is restricted by Parental Controls says he knows nothing about it. Also, now suddenly there's a Guest Account (disabled). How do I delete that? Am I being taken advantage of? Am I a Luddite or what? -mpdcleve

I think your kids may be a lot smarter with the Mac then you think. Try changing the Admin password again but this time use a strong password, one that the kids can't guess. Also make sure that if you're using Time Machine to backup your Mac, keep the backup drive out of the hands of the other users.