Did you restart the Flash installer after closing Firefox and making sure that firefox.exe process actually stopped and not 'hung' due to starting the Flash installer while Firefox was still running?

I used the task manager to close FF. I restarted Flash installer and it started to install again, and then stopped and asked to close FF. Keeps doing that over and over again.

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen or hold down the Shift key) to see if that makes it possible to install Flash.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

I restarted computer, then Real Player installed. Thanks for your replies.