I use Flash player from the first version of the software, so I'm not a newby.
But When I started the update, the regular first windows of the install frame is blank (dark grey, no widget inside)
I uninstalled fashplayer from my PC. I ran the test from this web page https://helpx.adobe.com/fr/flash-player.html
Flash Player is not detected. I ran the install problem with or without firefox up.
My configuration is Windows XP version 2002 service Pack 3
I'm administrator of my PC, so no access right problem.
I'm french, so sorry for my english, if something is understandable, warn me, I will try to be clearer.