What happened was that there was a problem with the screen which Apple was repairing under a program. We sent it in for repairs; they sent it back all set up with OSX, everything was new and all our previous data was lost. It was set up with Apple as the user, and I don't think there ever was another user--we didn't have any books or discs for OSX. We never had to choose a user when we were starting up, either, like we do on my husband's computer. We'd just push the button and eventually we'd be at the desktop.
So there may never have been another user.
And, (hitting myself on the forehead) I finally asked my sons what exactly happened: and this is it: last night, the little circle with a rainbow in it that turns round and round showed up, AFAIK while I was on a site that I go to (messageboard I have gotten hung up on before with my husband's computer)--well, apparently it just kept going all night long (I got interrupted and never got back to it) and this morning, what my 4yo was complaining about was just that. My other son went over and re-started the computer for him, and when it was re-started, the situation was as I described, but also, the background screen was reverted, as were the icons for folders and things. (The children are always changing the background, so I never pay attention to that).
So I guess that just being hung up all night or else whatever made it hang up was what did it.
If that makes you have more ideas, that would be great, but since that site has caused my husband's computer to hang up before, I think maybe it is a problem with the site...

I'm sorry I didn't get all this info in the first place, and I really appreciate your helping me out like this
