Unknown box appears on screen, won't go away.

Hello, I face a problem on windows7 laptop. A small box appears on the desktop screen.
It is actually my sisters device, I asked her to capture the screen and send it to me so I can post it. The box look like a blank window, its on the bottom left, covering the start button. Sometimes it doesn't appear at all, but when it does, it doesn't go away, I tried checking task manager for anything unusual, but the only thing that caught my attention is "atieclxx.exe", most likely irrelevant to the issue. It' doesn't look like a splash nor one of those ransomware windows. Any solutions?
Attaching screenshot. For discretion, I' ve covered parts of the image with black patches.
I 've never encountered this problem on my win7 devices.
Thanks in advance.


Update: Solved, It was avira. Got rid of it and installed ESET. Thanks to lehnerus2000 for suggesting Process Explorer.

I would try the following in order listed:

1. Right click the TaskBar and see if it is checked "Locked." If so left click to uncheck it to see if it fixes the issue.
2. Right click the TaskBar, left click "Properties", then click "Customize", then "Restore Default Icon Behaviors" to see if the issue is resolved.
3. Right click the TaskBar, left click Properties, then click the "Start Menu" Tab, then click "Customize" then click "Use Default Settings" to see if the issue is resolved.

Good luck and let us know how it turns out.

Process Explorer has a tool that you can use to identify the process associated with a window.

You can download it from here:
https://docs.microsoft.com/en-us/sys...ocess-explorer

It's a portable program (i.e. it doesn't install and you can run it from a USB stick). :)

1. Run the exe file (or unpack the zip file and then run the exe)
2. Drag the Crosshair icon over the mystery window and "drop it"
3. Check which process is highlighted

My screenshot shows that I dropped the Crosshair on the Pale Moon window.