Sometimes a window pops up with some information or an error message and it is not possible to identify which program or process created this window.
It is easy to identify the process that created any window using Process Explorer. Click on the crosshair icon in the toolbar. The mouse cursor changes to a crosshair and Process Explorer disappears. Move this cursor to the window you want to identify and release the mouse button. Process Explorer re-appears with the process that owns that window highlighted in its list.
Tried with: Process Explorer 15.2 and Windows 7 Enterprise x64