Why Does Windows Login Screen Continue Reappearing?

I'm using Windows 7 Pro. Until a few months ago, I could leave my desktop PC on overnight. As soon as I sat down and moved the mouse or tapped on a key on the keyboard, my screen saver would disappear and I could go right to work. It was great! Several months ago, a problem began that I'm about to describe.

Now when I walk away from my PC for a couple of hours and return, I see the Windows login screen. It does not happen all of the time, but it occurs the majority of the time.

My first step to remedy the problem was to check the Screen Setter settings. The screen setter ("Ribbons") is supposed to go on after 12 minutes of inactivity.
There's a box to the right of that setting that says "On resume, display login screen." This box is unchecked.
Next, I've adjusted the Power Settings to High Performance. The PC's display is set to Never for when to turn off the display and also Never for when to put the computer to sleep. I've then changed the advanced power settings in an attempt to remedy the problem. I've made sure that the following settings are as follows:
High Performance requires No password on wakeup.
Turn off hard disk after 800 minutes
Sleep Settings:
Sleep After = Never
Allow Hybrid Sleep = Off
Hybernate After = Never
Allow Wake Timers = Disable
Turn Off Display = Never
Power Button: Sleep Button Action = Do Nothing

For security reasons, I usually operate my PC as a standard user. But the Windows login screen keeps reappearing after I leave my PC for a while whether I'm running as limited user or as the Master Administrator.

Can you give me any additional ideas of what I can do to eliminate the Windows login screen from reappearing after I leave my PC?

1. I own the PC; I work from my home office and do both personal and business work on it.

2. I have a password for the user account and a separate password for the Master Administrator account.

I don't know; I'll try it. Is this step for diagnostic purposes or as a possible suggestion to resolve the issue? I ask because I believe that this shouldn't happen to the standard user account with or without a password.

Thanks Andrew. I've been swamped with work today, but I'll fiddle with this tomorrow and report back to you. There's something strange about this whole thing. I was logged in today as a user (NOT an Administrator or Master). I downloaded a Kindle program (an .exe file) from Amazon and I didn't need to login as an administrator to open it.

The reason I run Windows in the user mode instead of as an Administrator or Master is so a "bad guy" from the outside can't come in and take over my PC. I've been under the impression that if I'm running in regular user mode that I can't download and open .exe files like I can as an Administrator or Master. I know that this is not the topic of the thread that I initiated, but I wonder if this has any relationship with the login issue. Strange...

Some apps (like the installer for Chrome) will install as a standard user - never asking for admin permissions. When Chrome is installed by a non-admin, it skips setting up the scheduled tasks that checks for updates. The user probably has no idea that they are missing out on the automated update functionality :-(

I've seen your issue before - I just don't recall the fix (or if we ever found the fix). It started right after some Windows Updates on a computer that I support. I think that it eventually fixed itself after more OS updates.

Let's not mix instructions - in other words, please continue to follow andrew129260 instructions...
...but as a last resort:
place a check by the option to "On resume, display logon screen"
restart the computer and leave it overnight
then remove the check by the option to "On resume, display logon screen"
restart the computer and leave it overnight
This would be the "get Windows' attention" ploy.

If that fails, test with a new (temporary) user profile.