How can I do if my PC Black Screen?

This usually points to a Windows shell or graphics issue caused by the update, especially since Task Manager still opens. A few things you can try:

• From Task Manager → File → Run new task, type explorer.exe and press Enter. If the desktop loads, it’s likely Explorer failing to start.
• If that doesn’t help, boot into Safe Mode and uninstall the most recent Windows update on both systems.
• Also check Display Drivers in Device Manager—updates sometimes break GPU drivers. Rolling back or reinstalling them often fixes the black screen with cursor issue.
• As a last step, run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth from an admin Command Prompt.

Since it’s happening on two machines after updates, I’d strongly suspect a bad update or driver conflict rather than hardware failure.