Log on Screen Keeps Popping up

I don't know what I did but recently, my log-on screen with my picture on it pops up all the time. It is in a locked state (dont know how that happened either) and has a "Switch User" tab beneath it. It pops up when I am playing an online game which is very irritating. I am the only one who uses this computer so I have my login marked as "Administrator". What do I do to fix this? Thankyou in advance.

You could try a System Restore point. Try the day before it started.
Easy and you won't loose any info. Put a check mark in "Show other restore points" if needed when this window opens.
Mike

Just in case.
http://www.sevenforums.com/tutorials/700-system-restore.html