A random transparent rectangle on the screen

[Aaron0301]

see it? next to the taskbar

 

[Trouble]

I'm gonna say that, that's something running at start up. It almost looks like a transparent Sticky Note
Check the Startup Tab in Task Manager
IF no joy, then do a clean boot

How to perform a clean boot in Windows - Microsoft Support

Describes how to use the clean boot process to troubleshoot a problem in Windows 8.1, Windows 8, Windows 7, or Windows Vista.

support.microsoft.com