If you are reading this on a computer, it's a sure bet that Adobe's Flash Player is installed. A couple days ago, Adobe released a new version of the Flash Player web browser plugin and there are few things you need to know to upgrade correctly.
To confirm that you need an upgrade, point your browser to adobe.com/products/flash/about. The just-released version of the Flash Player is 22.214.171.124. The prior version, 126.96.36.199, was released in December 2007. Each web browser installed on your computer is a free agent (so to speak) so you need to check each one to know if an upgrade is needed.
If you need to upgrade, don't, not yet.
The Flash installer has a long history of not removing older versions. Since it's never good to have buggy software on your computer, the first step to upgrading the Flash Player is removing any and all prior versions. Windows users can get a report of all copies of the Flash player from the free online Secunia Software Inspector. I suggest opting for the "thorough system inspection". Recently, on a brand new computer, Secunia found a copy of the downright ancient Flash Player version 6.
Firefox users on Windows will have two copies of the Flash player. Adobe packages Flash as an ActiveX control for Internet Explorer and as a "plugin" for Firefox, Opera, Netscape and Mozilla.
There are three ways to uninstall the Flash player, the normal way, the manual way and the recommended way.
For Windows users, the normal way is, of course, the "Add or Remove Programs" thingy in the Control Panel. In the past, this has not been reliable.
Instead, I suggest downloading Adobe's Flash Player uninstaller which, quoting Adobe, "will remove Adobe Flash Player from all browsers on the system." A new version of the uninstaller was released on April 8th. Good thing too, as the prior version had some issues. You can read about the Flash Player uninstaller here. There is a version for Windows, a version for Mac OSX and another version for Mac OS8 and OS9. Linux users can find both install and un-install instructions at the Adobe Flash Player for Linux Readme
The Flash uninstaller needs some care and feeding. Adobe warns that it can not remove in-use files, so they advise quitting ALL running applications. They also warn that "Internet Explorer users may have to reboot to clear all uninstalled Flash Player ActiveX control files. If you're not certain, select the "Show Details" button in the Flash Player uninstaller. If there are any log lines that begin with "Delete on Reboot..." then you'll need to reboot BEFORE running the Flash Player installer again."
Below is a screen shot of the Flash Player uninstaller:
After running the uninstaller, I suggest that Windows users run a "thorough" scan with the Secunia Software Inspector to insure that all versions were really removed. Any instance of the Flash Player that was left behind is a candidate for manual removal. As show below, Secunia points you directly to the offending file(s).
In my experience, the Flash Player has always been a single file. Renaming or deleting the file should logically uninstall it. If you opt to rename it, be sure to change the file type. I got burned recently when I changed the file name but left the file type unchanged. For example, to rename x.dll, use x.dll.DONTUSEME rather than x.DONTUSEME.dll.
You can get the latest version of the Flash Player at www.adobe.com/go/getflash. The web page detects your operating system and browser and offers the correct version of the software automatically.
Internet Explorer users get an option that Firefox users (on Windows) do not - also installing the Google Toolbar. There is no need to install the Google software. In general, if software companies offer to throw-in extra stuff for free, it's to their benefit, not yours.
The install process, in Windows, is very different for Internet Explorer and Firefox. The Internet Explorer installation is done within the browser. The Flash Player is an ActiveX control, so you will likely have to approve the yellow toolbar warning and then again approve the installation in a pop-up window.
The Firefox install starts with downloading an installer file (install_flash_player.exe). Then you have to shut down Firefox and run the installer. When it's done, you should see something like the screen shot above. At this point, I suggest taking Firefox on a visit to the Adobe Flash tester page to insure that everything went according to plan.
As I write this, I've upgraded just a couple machines. One Windows XP machine had version 188.8.131.52 of the Flash Player and, in the interest of research, I installed the latest version directly on top of the old version. It failed, as you can see in the screen shot below. However, re-running the installer worked fine.
The Flash Player may well be the most widely used software in the world. Make sure your copy is up to date.
Update April 11, 2008: Someone commented below that the Flash uninstaller failed to remove old copies of version 6 and 7 that a "thorough system inspection" with the Secunia Software Inspector found. I can't confirm this, so if you find these old versions of the Flash player, please let me know your experience, either with a comment below or send me an email at my personal website, michaelhorowitz.com.
Update April 12, 2008: If Firefox seems to be using the wrong version of the Flash Player, or any other plugin, see Tracking down Firefox plugins.