User accounts I didn't create showing up

I recently discovered two new user accounts on my computer and no idea how they got there. They have weird names - A65AECA2A06F4887AB01 and AE2640E6361B4955B852. They are standard users and it appears they were created 4 minutes ago. I use Norton 360 and I do not use wifi. I do virtually no downloads and rarely accept attachments from anyone. I'm on Windows 7. These accounts show up under control panel but if you try to switch users, only my administrative and non-admin accounts show up. How can I understand where these accounts came from?

Ok so I did learn a few interesting things as I went back and studied this further. The two mysterious user accounts only show up under Parental Controls. They are standard user, password protected accounts. For the life of me, I can't figure out how they got there. Nobody uses this computer except for me. Looking through the event logs but don't see anything as of yet. To what extent, if any, does that change the calculus that they are only under parental controls?

Oh my Norton 360 is up to date. Thanks!

How do you determine which programs can create user accounts? Better yet, how do you block all from being able to do this?

These accounts show up under parental controls - how do I get rid of them?