Here is another thing you can try.
Download
Process Monitor. Run as admin.
Go to Filter > Filters... and add "Operation is Process Start then Include". Delete any other filters that are set to "Include".
You will see an entry every time a new process is launched on your PC. You can leave this running a while I guess and wait for a while until the window you're looking for starts. Try to note the exact time (to the second) on your system clock when it launched. Then click the "Capture" button in the toolbar to stop capturing. (While waiting for the program to run you may want to periodically hit "Clear" on the toolbar to clear old entries; the program could use up quite a bit of memory if you leave it running for a long time).
In the main window you'll see the command line of the process, and parent PID (process ID). You can then go to Task Manager and find the PID to see which process is launching it.
This might help track it down.