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Note: The about:plugins list is generated from data stored in the "pluginreg.dat" file.  To refresh the list, close the browser and delete the "pluginreg.dat" file, located in the profile folder in current Mozilla browsers.To install Flash or to update to the latest version for your operating system, visit the Adobe Flash Player Download Center (see the system requirements and FAQ pages for more information).Adobe has recently started to bundle other applications from other vendors with the download so make sure to opt out of any programs or tools you don't want before clicking the button.
In current versions, the INSTALL button is disabled until you check-mark the box in the Adobe Flash Player installation dialog where it says, "I have read and agree to the terms of the license agreement".   You can install or update Flash by downloading the plugin installer from Adobe's Flash Player download page or from the Adobe Flash Player Distribution page.