I have tried downloading Flash player multiple times. It will get to the very end, but then will not open or work when I try to use a program that requires it. The last time I tried to download it, after it told me that it was complete, a screen popped up that said only one instance could run. I am not sure how to fix this problem.
Download the Adobe Flash Player uninstaller and installers directly by right clicking the following links and selecting "Save target as" (IE) or "Save Link as"(Firefox).
Save the files to your Downloads folder - DO NOT run anything yet.
Reboot your system.
BEFORE opening anything, go to the Downloads folder and run the UNINSTALLER to remove all instances of Flash Player.
Next, run the ActiveX installer, and then the (other browsers) Installer.