If you share your computer with a teenager, you may have this problem. When the teenager has finished doing whatever teenagers do on computers, he is likely to log out by simply switching users, since this keeps programs in memory, and makes it much faster when he comes back from wherever teenagers go when they are not sitting in front of a computer.
But for us civilized adults, it's a PITA because only one person can be logged into iTunes at a time, so unless you can access the teenager's account (unlikely) you can't run iTunes if he left it running.
So several years ago, I found this registry hack which simply gets rid of the option to switch users. Having applied it, I never had a problem again.
Here are detailed instructions. Remember to back up the registry before you play around in there.
http://www.askvg.com/how-to-disable-switch-user-option-in-windows-vista-and-7/
But for us civilized adults, it's a PITA because only one person can be logged into iTunes at a time, so unless you can access the teenager's account (unlikely) you can't run iTunes if he left it running.
So several years ago, I found this registry hack which simply gets rid of the option to switch users. Having applied it, I never had a problem again.
Here are detailed instructions. Remember to back up the registry before you play around in there.
http://www.askvg.com/how-to-disable-switch-user-option-in-windows-vista-and-7/