Okay, I think the PyInstaller folks correctly identified the issue, which is simply that Python 3.9 dropped Windows 7 support. I've added a new download to the main page here for a version 9.17.1b (note the b) made with Python 3.8.10. Please try that and let me know if that runs on your system. If so, I'll make sure to do future builds with 3.8 for as long as I can (Python says they'll support 3.8 until 2024).