I tried to update my old version of flash. I downloaded the most recent version to my download file and its there. When I double click on it to install nothing happens? I have tried the download several times and it still wont open and install? I am running an older version of XP and using firefox as a browser. Can anyone help. I cant view any streaming video without it. Thank you in advance for any help you can provide.
If you're not running Windows XP Service Pack 3, you'll need to upgrade at least to XP SP3, because XP lacks support for the bare-minimum cryptographic technologies necessary to sign binary installers in 2015. You're also missing about 15 years worth of modern security mitigations in the operating system itself. Taking over a windows XP machine perfectly and silently is trivial at this point, which is why we need to move the world off of it.
If you're on XP SP3 already, I'd start by rebooting. If that doesn't help, I'd look at any third-party anti-virus applications you may have installed. They may be erroneously blocking the installer.
If that doesn't work, I'd probably run the disk repair utilities (scandisk and defrag), delete the installer you downloaded, reboot, download a fresh installer from http://get.adobe.com/flashplayer/.